msvs: Revert r1920 and add a test for excluded idl

The test uses a "bad" idl to verify that it gets excluded from the msvs build.
If it doesn't get excluded, then the build will fail because the bad.idl is
syntactically wrong.

BUG=
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/307953002

git-svn-id: http://gyp.googlecode.com/svn/trunk@1925 78cadc50-ecff-11dd-a971-7dbc132099af