Include PathV1.h in files that use it.

This is preparation for replacing Path.h with PathV2.h.

llvm-svn: 183781
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 6af3663..3b75790 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/PathV1.h"
 #include "llvm/Support/system_error.h"
 #include <sys/stat.h>
 using namespace clang;