Split uninit analysis from predicate analysis

Split uninit analysis from predicate analysis

This splits the API collected in gimple-predicate-analysis.h into
what I'd call a predicate and assorted functionality plus utility
used by the uninit pass that happens to use that.  I've tried to
be minimalistic with refactoring, there's still recursive
instantiation of uninit_analysis, the new class encapsulating a
series of uninit analysis queries from the uninit pass.  But it
at least should make the predicate part actually reusable and
what predicate is dealt with is a little bit more clear in the
uninit_analysis part.

I will followup with moving the predicate implementation bits
together in the gimple-predicate-analysis.cc file.

	* gimple-predicate-analysis.h (predicate): Split out
	non-predicate related functionality into ..
	(uninit_analysis): .. this new class.
	* gimple-predicate-analysis.cc: Refactor into two classes.
	* tree-ssa-uninit.cc (find_uninit_use): Use uninit_analysis.