[Tooling] Parse compilation database command lines on Windows.

When a compilation database is used on Windows, the command lines cannot
be parsed using the standard GNU style syntax. LLVM provides functions for
parsing Windows style command lines, so use them where appropriate.

After this patch, clang-tidy runs correctly on Windows.

Reviewed by: alexfh
Differential Revision: https://reviews.llvm.org/D23455

llvm-svn: 278964