[Win] IDLParser.pm fails to parse OESTextureHalfFloat and causes a build failure
https://bugs.webkit.org/show_bug.cgi?id=111267

Reviewed by Kentaro Hara.

Allow empty definitions.

* bindings/scripts/IDLParser.pm:
(Parse):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144575 268f45cc-cd09-0410-ab3c-d52691b4dbfc