* ctype/ctype.h (isblank): Make available if ISO C99.
* wctype/wctype.h (iswblank): Make available if ISO C99.
* math/math.h (signgam): Don't make available if ISO C99.
* math/tgmath.h (tgamma): Renamed from gamma.
Patches by Joseph S. Myers <jsm28@cam.ac.uk>.