[Windows, WinCairo] Remove pthread paths for WebKit build.
https://bugs.webkit.org/show_bug.cgi?id=115390

Reviewed by Tim Horton.

Update Visual Studio property sheets to remove include paths and
link references for the pthreadsVC2.dll, which is no longer used.

../WebKit: 

* WebKit.vcxproj/WebKit/WebKitCommon.props:
* WebKit.vcxproj/WebKitExportGenerator/WebKitExportGeneratorCommon.props:

../WebKit/win: 


* WebKit.vcproj/WebKitExportGeneratorCommon.vsprops:
* WebKit.vcproj/WebKitLibCommon.vsprops:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149385 268f45cc-cd09-0410-ab3c-d52691b4dbfc