Improve existing functionals:
  *) Add XC_FLAGS_STABLE or XC_FLAGS_DEVELOPMENT to all functionals in libxc.

Add functionals:

LDA:
 *) Short-range LDA correlation functional (Phys. Rev. B 73, 155111 (2006))
 *) Short-range exchange 10.1080/00268979609484488

GGAs:
  *) Tozer, Ingamells and Handy neural network potential JCP 105, 9200 (1996); doi: 10.1063/1.472753
  *) http://dx.doi.org/10.1063/1.3243845 Missing are: CS1, wPBE, WI, W1, W2, Wl, bPBE, qPBE, rPBE, A1, A2, A3, WLV.
  *) df-LB94, df-revLB94 http://dx.doi.org/10.1103/PhysRevA.83.012509
  *) Lambda-LB94, Q-LB94, Q-revLB94  http://dx.doi.org/10.1063/1.3684261
  *) Gilbert and Gill c [CPL 312, 511 (1999)] http://www.sciencedirect.com/science/article/pii/S0009261499008362
  *) BNL (Baer-Neuhauser-Livshits) [Phys. Rev. Lett. 94, 043002 (2005) and Phys. Chem. Chem. Phys. 9, 2932 (2007)] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.94.043002 and http://pubs.rsc.org/en/content/articlelanding/2007/cp/b617919c
  *) B97GGA-1 and B97-1b (A.J.Cohen,N.C.Handy, Chem.Phys.Lett., 316,160 (2000)) This is a different version of B97-1!!!
  *) B98-1, and VS98-1	(A.J.Cohen,N.C.Handy, Chem.Phys.Lett., 316,160 (2000))
  *) GDS08 KED functional http://dx.doi.org/10.1103/PhysRevB.77.073104
  *) GHDS10 KED functional http://dx.doi.org/10.1063/1.3280953
  *) GHDS10 reparametrized and TKVln http://dx.doi.org/10.1103/PhysRevB.84.075146
  *) https://repository.aust.edu.ng/xmlui/bitstream/handle/123456789/549/Iyomo%20Irewole.pdf?sequence=1&isAllowed=y Equation (3.36)
  *) ZLP2 (https://journals.aps.org/pra/pdf/10.1103/PhysRevA.47.918 Eq. (21), and at the end there are several kinetic contributions to the correlation energy) and k (Chem. Phys. Lett. 232, 31)
  *) KT3 http://aip.scitation.org/doi/10.1063/1.1784777
  *) OF https://aip.scitation.org/doi/full/10.1063/1.5025171 

mGGAs:
  *) regTPSS exchange http://pubs.acs.org/doi/abs/10.1021/ct300269u
  *) KCISK 10.1063/1.1390178 i.e. Krieger2001_48
  *) hybrids in http://scitation.aip.org/content/aip/journal/jcp/112/9/10.1063/1.480951
  *) tau-PBE (http://scitation.aip.org/content/aip/journal/jcp/111/3/10.1063/1.479374)
  *) ISM (http://scitation.aip.org/content/aip/journal/jcp/116/15/10.1063/1.1462618)
  *) LAP class of functionals [70]
  *) PK06 (part of the LAP class of functionals) http://dx.doi.org/10.1021/ct600372t
  *) MCY1 and MCY2 http://dx.doi.org/10.1063/1.2179072
  *) spin-polarized Colle-Salvetti -type correlation http://www.sciencedirect.com/science/article/pii/S0009261497002017
  *) B94 [A. D. Becke, Int. J. Quantum Chem. Symp. 28, 625 (1994) and  E. Proynov, Z. Gan, and J. Kong, Chem. Phys. Lett. 455, 103 (2008)]
  *) Laplacian-level KED functional from Salazar et al http://dx.doi.org/10.1002/qua.25179
  *) L0.4 and L0.6 ( S. Laricchia, E. Fabiano, L. A. Constantin, F. Della Sala,
!           J. Chem. Theory Comput. 10, 164 (2014). )
     http://www.theory-ecmt.it/nnldft_web/lkin.txt
  *) 2D exchange functional of https://arxiv.org/pdf/1703.01728.pdf
  *) Lap3 correlation http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1097-461X(1997)64:4%3C427::AID-QUA5%3E3.0.CO;2-Y/full
  *) tau1 functional (modified Becke exchange already implemented) http://aip.scitation.org/doi/abs/10.1063/1.1321309

hybrids:
  *) doi:10.1021/ct800530u (LR-omegaPBE08)
  *) http://dx.doi.org/10.1021/ct300715s
  *) (CAM-)S12g / (CAM-)S12h http://www.sciencedirect.com/science/article/pii/S0009261413008221
  *) HISS http://scitation.aip.org/content/aip/journal/jcp/127/22/10.1063/1.2822021 [*two* range separation constants!)
  *) hAPBE DOI: 10.1021/ct500902p
  *) rCAM-B3LYP http://aip.scitation.org/doi/abs/10.1063/1.2741248
  *) WC04 and WP04 http://pubs.acs.org/doi/abs/10.1021/ct6001016
  *) CAM-LDA0 http://pubs.acs.org/doi/abs/10.1021/acs.jpca.5b10864

hybrid meta:
  *) b1b95 (54, 60)
  *) dispersion corrected wB97X
     http://pubs.rsc.org/is/content/articlelanding/2008/cp/b810189b
  *) long-range Minnesota hybrids
     wM05-D http://aip.scitation.org/doi/abs/10.1063/1.4704370
     wM06-D3 and wB97X-D3 http://pubs.acs.org/doi/abs/10.1021/ct300715s
  *) http://pubs.acs.org/doi/abs/10.1021/jp050036j (TPSS0?)
  
local hybrids:
  *) Jaramillo et al, J. Chem. Phys. 118, 1068 (2003), doi 10.1063/1.1528936
  *) Becke, J. Chem. Phys. 119, 2972 (2003), doi 10.1063/1.1589733
  *) Arbuznikov and Kaupp, Chem. Phys. Lett. 440, 160 (2007),
     doi 10.1016/j.cplett.2007.04.020
  *) Bahmann et al, J. Chem. Phys. 126, 011103 (2007), doi 10.1063/1.2429058
  *) Janesko et al, J. Chem. Phys. 129, 124110 (2008), doi 10.1063/1.2980056
  *) Perdew et al, Phys. Rev. A 78, 052513 (2008),
     doi 10.1103/PhysRevA.78.052513
          and
     Jiménez-Hoyos et al, Mol. Phys. 107, 1077 (2009),
     doi 10.1080/00268970902740555
  *) Haunschild et al, J. Chem. Phys. 131, 154112 (2009),
     doi 10.1063/1.3247288
  *) Arbuznikov et al, J. Phys. Chem. A 113, 11898 (2009),
     doi 10.1021/jp903233q
  *) Haunschild and Scuseria, J. Chem. Phys. 132, 224106 (2010),
     doi 10.1063/1.3451078
  *) Johnson, J. Chem. Phys. 139, 074110 (2013), doi 10.1063/1.4818454
  *) Schmidt et al, J. Chem. Phys. 140, 18A510 (2014), doi 10.1063/1.4865942
also possibly the following
- V. V. Karasiev, J. Mol. Struct. (THEOCHEM), 493, 21 (1999).
- V. V. Karasiev and E. V. Ludeña, Phys. Rev. A 65, 062510 (2002).
- V. V. Karasiev and E. V. Ludeña, Phys. Rev. A 65, 032515 (2002).


54: Becke, A. D. Phys. ReV. A 1988, 38, 3098.
60: Becke, A. D. J. Chem. Phys. 1996, 104, 1040.
67: Rey, J.; Savin, A. Int. J. Quantum Chem. 1998, 69, 581.
68: Kreiger, J. B.; Chen, J.; Iafrate, G. J.; Savin, A. In Electronic
    Correlations and Materials Properties; Gonis, A., Kioussis, N., Eds;
    Plenum: New York, 1999; p 463.
    http://dx.doi.org/10.1007/978-1-4615-4715-0_28
69: Toulouse, J.; Savin, A.; Adamo, C. J. Chem. Phys. 2002, 117, 1441.
70: http://dx.doi.org/10.1016/0009-2614(94)01189-3
    http://dx.doi.org/10.1002/qua.560560808
    http://dx.doi.org/10.1002/(SICI)1097-461X(1997)64:4<427::AID-QUA5>3.0.CO;2-Y
    http://link.aip.org/link/doi/10.1063/1.1321309
