Do not register edges for statements not understood.

Do not register edges for statements not understood.

Previously, all gimple_cond types were undserstoof, with float values,
this is no longer true.  We should gracefully do nothing if the
gcond type is not supported.

	PR tree-optimization/106510
	gcc/
	* gimple-range-fold.cc (fur_source::register_outgoing_edges):
	  Check for unsupported statements early.

	gcc/testsuite
	* gcc.dg/pr106510.c: New.