Globally ignore '*_excluded' keys for MSVS Settings

This extends validation of MSVS settings to ignore any key found that is suffixed with '_excluded', but still verifies that the root key name is a valid setting.

Patch from Eric N. Vander Weele <ericvw@gmail.com>

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/175873002

git-svn-id: http://gyp.googlecode.com/svn/trunk@1858 78cadc50-ecff-11dd-a971-7dbc132099af
Clean up the filters in the MSVS generator, for VS >= 2010

Addendum to r1804. The fix in that revision only works
for VS 2008; for 2010 and later we generate one filter
per source file, so in order to clean these up, we must
prune sibling filters as long as they all have the same
name.

Patch by stk.haller@googlemail.com.

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/171713013

git-svn-id: http://gyp.googlecode.com/svn/trunk@1859 78cadc50-ecff-11dd-a971-7dbc132099af