With the new update to the ABI, we should not look for installations

of MinGW older than 4.7 with incompatible C++ libraries.

This patch makes clang look for all MinGW versions from 4.7:

  4.7.0, 4.7.1, 4.7.2, 4.7.3
  4.8.0, 4.8.1, 4.8.2.

llvm-svn: 197176