Use a slightly more liberal regex to detect Visual Studio version

Use a slightly more liberal regex to detect Visual Studio version

Apparently in some language versions of Visual Studio nmake outputs some
material after the version number and before the end of the line. This
has been seen in Chinese versions. Therefore, we no longer demand that
the version string comes at the end of a line.

Per complaint from Cuiping Lin.

Backpatch to all live branches.