stdint: Verify the width of 'long long' before using it as int64_t. Suggested by Paul Eggert in <https://lists.gnu.org/archive/html/bug-gnulib/2024-05/msg00315.html>. * lib/stdint.in.h (gl_int64_t): Verify that the number of bits of 'long long' is 64 before using it. (gl_uint64_t): Verify that the number of bits of 'unsigned long long' is 64 before using it.