Improve dependency file support.

Improve dependency file support.
 - Rip out various bits of logic from clang-cc's dependency file gen,
   force driver to provide instead.

 - -MD output now goes to proper location
<rdar://problem/6723948> clang -MD puts dep file in /tmp with wrong name

 - -M and -MM still don't work correctly.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@68022 91177308-0d34-0410-b5e6-96231b3b80d8