middle-end/114070 - folding breaking VEC_COND expansion

The following properly guards the simplifications that move
operations into VEC_CONDs, in particular when that changes the
type constraints on this operation.

This needed a genmatch fix which was recording spurious implicit fors
when tcc_comparison is used in a C expression.

	PR middle-end/114070
	* genmatch.cc (parser::parse_c_expr): Do not record operand
	lists but only mark operators used.
	* match.pd ((c ? a : b) op (c ? d : e)  -->  c ? (a op d) : (b op e)):
	Properly guard the case of tcc_comparison changing the VEC_COND
	value operand type.

	* gcc.dg/torture/pr114070.c: New testcase.