Make -include, -imacros paths absolute in Frontend.  - Otherwise paths will be resolved relative to the main input file,    which is incorrect.
Make -include, -imacros paths absolute in Frontend.
 - Otherwise paths will be resolved relative to the main input file,
   which is incorrect.

 - I don't know how to make a reasonable test case for this with our
   testing infrastructure.

 - PR3395


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@68665 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang