In MemoryDependenceAnalysis::getNonLocalPointerDepFromBB, if a given block is...

In MemoryDependenceAnalysis::getNonLocalPointerDepFromBB, if a given block is is deemed unanalyzable (and we execute one of the "goto PredTranslationFailure" statements), make sure we don't put information about the predecessors of that block into the returned data structures; this can lead to, among other things, extraneous results (which will confuse passes using memdep).  Fixes an assert in GVN compiling ruby. Part of rdar://problem/9521954 .

Testcase coming up soon.

llvm-svn: 132434