Remove last use of PathV1.h from clang.

Instead of creating a temporary directory, remember the set of temporary files
we create.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184951 91177308-0d34-0410-b5e6-96231b3b80d8
clang/test/Driver/pth.c: Fix r184942, a regexp like "\\\\" is redundant here. Should be matched to single \ with '\\'.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184952 91177308-0d34-0410-b5e6-96231b3b80d8