Improve overflow check

Convert
x < (short) ((unsigned short)x + const)
to
x <= SHORT_MAX – const
(and similarly for other integral types) if const is not 0.

gcc/
	PR tree-optimization/97223
	* match.pd (overflow detection and optimization): Handle conversions.

gcc/testsuite/

	* gcc.dg/no-strict-overflow-4.c: Adjust expected output.