doc: mention glibc, OS X, Cygwin [S]SIZE_MAX buglet More platforms have similar bugs, and in the case of glibc on s390, the bug is in SIZE_MAX instead of SSIZE_MAX. * doc/posix-headers/stdint.texi (stdint.h): Document the bugs. * doc/posix-headers/limits.texi (limits.h): Document the bugs. Signed-off-by: Eric Blake <eblake@redhat.com>