Add Configure symbols to all the missing C99 math APIs.

Almost all - e.g. isless() will stand in for the other isfoo()
order comparison macros.

Also not going for all the *l() versions of each interface.
checkcfgvar.pl --regen --default=undef; make regen
VMS configure.com C99 math symbols
AIX: Configure now detect this, leave the comment.

(Some AIX do not have long double math interfaces.)
The NO_C99_LONG_DOUBLE_MATH is no more used.
Make the C99 *l test a little bit more accepting.
quadmath has tgammaq, not tgammal.
Remove unneeded HP-UX cases.
Only #ifndef gcc cases remain.
Remove trivial unneeded cases of not having C99 math.
Android should be doing the Configure scans.
We now have symbols for llrint and llround.
VMS should now be handled.
Remove unneeded Tru64 cases.
Tru64 more undef hints.
Remove now empty case.
cosh and log10 are already C89.
undef c99_foo ifndef HAS_FOO
Remove unneeded Win32 cases.
Remove Cygwin cases.  Case.