[Info-vax] Old work-arounds v. new <stdint.h> (et al.)

[Steven Schweda]

   Some of my old work-arounds for missing <stdint.h> (and its friends),
for example, my declarations of [u]intmax_t, now conflict with those in
the new <stdint.h>.

   Is there a C macro which would reveal whether <stdint.h> exists,
and/or <inttypes.h> has some actual content, and so on?  Perhaps a test
like: "__STDC_VERSION__ >= 199901"?

   Here, "new" means something like "VSI C V7.4-001 on OpenVMS IA64
V8.4-2L3", and "not new" would be something from HP[E] which I can't
easily run now.  I'd prefer to keep things working in older
environments, but I might be too lazy to use a "configure" script to
deal with this stuff.

   Is there some documentation where I should have found this already?