Really remove ENABLE_PLUGIN_PROXY_FOR_VIDEO

Really remove ENABLE_PLUGIN_PROXY_FOR_VIDEO
<http://webkit.org/b/132432>

Reviewed by Tim Horton.

.:
* Source/cmake/WebKitFeatures.cmake:
* Source/cmakeconfig.h.cmake:
- Remove ENABLE_PLUGIN_PROXY_FOR_VIDEO as build option.

Source/WebCore:
* platform/graphics/wince/MediaPlayerPrivateWinCE.h: Remove
methods and ivar in ENABLE(PLUGIN_PROXY_FOR_VIDEO).

Tools:
* Scripts/webkitperl/FeatureList.pm: Remove support for
--plugin-proxy-for-video switch.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@168109 268f45cc-cd09-0410-ab3c-d52691b4dbfc