Fix crashes when creating global instances of polymorphic classes without fields

Reviewed at http://llvm-reviews.chandlerc.com/D1795

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191839 91177308-0d34-0410-b5e6-96231b3b80d8
Objective-C migrator. Simplify migrator option 
processing in preparation for adding several more
options. // rdar://15003157


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191842 91177308-0d34-0410-b5e6-96231b3b80d8
Speed up CorrectTypo by avoiding lookups on unreasonable candidates.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191846 91177308-0d34-0410-b5e6-96231b3b80d8