Add support for armv7-windows-gnu targets to the clang front end.
Relative LLVM review
http://reviews.llvm.org/D11075
Windows only supports Little endian so it made more sense to have the naming reflect this.
It was confusing looking through the source to see that darwin arm targets did not specify endianess because they only support one yet we were specifying for itanium arm on windows.
I fixed that in the patch also