Add a != MIN/MAX_VALUE_CST ? CST-+1 : a to minmax_from_comparison

Add a != MIN/MAX_VALUE_CST ? CST-+1 : a to minmax_from_comparison

This patch adds the support for match that was implemented for PR 87913 in phiopt.
It implements it by adding support to minmax_from_comparison for the check.
It uses the range information if available which allows to produce MIN/MAX expression
when comparing against the lower/upper bound of the range instead of lower/upper
of the type.

minmax-20.c is the new testcase which tests the ranges part.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

	* fold-const.cc (minmax_from_comparison): Add support for NE_EXPR.
	* match.pd ((cond (cmp (convert1? x) c1) (convert2? x) c2) pattern):
	Add ne as a possible cmp.
	((a CMP b) ? minmax<a, c> : minmax<b, c> pattern): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/minmax-22.c: New test.