Driver.cpp: Restore clang/Config/config.h to be included at last not to prevent llvm-config.h.
Driver.cpp: Restore clang/Config/config.h to be included at last not to prevent llvm-config.h.

Or "llvm/Support/system_error.h" could not be compiled on mingw.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@169354 91177308-0d34-0410-b5e6-96231b3b80d8

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