GCStrategy should not own GCFunctionInfo

This change moves the ownership and access of GCFunctionInfo (the object which describes the safepoints associated with a safepoint under GCRoot) to GCModuleInfo. Previously, this was owned by GCStrategy which was in turned owned by GCModuleInfo. This made GCStrategy module specific which is 'surprising' given it's name and other purposes.

There's a few more changes needed, but we're getting towards the point we can reuse GCStrategy for gc.statepoint as well.

p.s. The style of this code ends up being a mess. I was trying to move code around without otherwise changing much. Once I get the ownership structure rearranged, I will go through and fixup spacing, naming, comments etc.

Differential Revision: http://reviews.llvm.org/D6587