Make signness explicit in tree-ssa/pr102736.c

This test is failing on ppc64* due to different default signness for
chars.

Tested on x86-64 Linux and ppc64le Linux.

	PR testsuite/pr102751

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr102736.c: Make sign explicit.
1 file changed