Moved Google Test code up one directory so that we can use a standard LLVM

Moved Google Test code up one directory so that we can use a standard LLVM
Makefile with it, without resorting to the use of VPATH.

Also added Makefiles at every level of the directory tree to properly recurse
to Google Test and build it as a library (original Makefiles by Talin).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61539 91177308-0d34-0410-b5e6-96231b3b80d8