Remove GENERIC expr building from predicate analysis, improve dumps

The following removes duplicate dumping and makes the predicate
dumping more readable.  That makes the GENERIC predicate build
routines unused which is also nice.

	* gimple-predicate-analysis.cc (dump_pred_chain): Fix
	parentizing and AND prepending.
	(predicate::dump): Do not dump the GENERIC expanded
	predicate, properly parentize and prepend ORs to the
	piecewise predicate dump.
	(build_pred_expr): Remove.