Fix a crash in the assumption cache when inlining indirect function calls

Summary:
Instances of the AssumptionCache are per function, so we can't re-use
the same AssumptionCache instance when recursing in the CallAnalyzer to
analyze a different function. Instead we have to pass the
AssumptionCacheTracker to the CallAnalyzer so it can get the right
AssumptionCache on demand.

Reviewers: hfinkel

Subscribers: llvm-commits, hans

Differential Revision: http://reviews.llvm.org/D7533

llvm-svn: 228957