Revert most of r82198, which was causing a large number of crashes

when running the analyzer on real projects.  We'll keep the change to
AnalysisManager.cpp in r82198 so that -fobjc-gc analyzes code
correctly in both GC and non-GC modes, although this may emit two
diagnostics for each bug in some cases (a better solution will come
later).

llvm-svn: 82201