deref-before-check-pr113253.c: Fix bogus warnings on lp32

deref-before-check-pr113253.c: Fix bogus warnings on lp32

Warnings about pointer sizes cause the test to fail
incorrectly. A dummy return value is also added to
set_marker_internal for completeness to suppress a
-Wreturn-type warning even though gcc does not issue
it by default.

Signed-off-by: Jonathan Yong <10walls@gmail.com>
gcc/testsuite/ChangeLog:

	PR analyzer/113253
	* gcc.dg/analyzer/deref-before-check-pr113253.c:
	(ptrdiff_t): use stddef.h type.
	(uintptr_t): ditto.
	(EMACS_INT): ditto.
	(set_marker_internal): Add dummy 0 to suppress -Wreturn-type.