[include-fixer] Don't return a correction if the header insertion failed.
[include-fixer] Don't return a correction if the header insertion failed.

This is could happen in cases involving macros and we don't want to
return an invalid fixit for it or a confusing error message with no
fixit.

git-svn-id: a34e9779ed74578ad5922b3306b3d80a0c825546@292405 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra