updates

[Guido Draheim]

ax_cflags_strict_prototypes - updated
ax_cflags_no_writable_strings - updated
ac_create_stdint_h - updated
ac_cond_with - marked obsolete
ax_cflags_gcc_option - added to C_Support
ax_enable_builddir - added to Miscellaneous

Those have been in the sf branch for a while and
I've been using them in a few projects so they
should have not that many bugs ;-) I'll leave the
other new ones of mine for a bit of further testing
as experimental.

I'm preparing a release of the sf archive, I think
that the ac-archive idea should get another round
of visibility raising. I still do not know the
current status of the gnu ac-archive and the works
on its release infrastructure, please give me a
hint somewhen during the next days. Thanks. -- guido