Suggest including <stdint.h> or <cstdint> for [u]int[8|16|32|64]_t

Plus [u]intptr_t and associated constants.

Refactor the bool, true, false, <stdbool.h> code so it fits into the
new table based design.

gcc/c-family/ChangeLog:

	* known-headers.cc (get_stdlib_header_for_name): Add a new
	stdlib_hint array for stdbool and stdint.

gcc/testsuite/ChangeLog:

	* gcc.dg/spellcheck-stdint.c: New test.
	* g++.dg/spellcheck-stdint.C: Likewise.