Fix a nasty corner case that Neil noticed in PR1900, where we would 
incorrectly apply the multiple include optimization to files with 
guards like:

#if !defined(x) MACRO

where MACRO could expand to different things in different contexts.
Thanks Neil!



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@45716 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed