Reviewed by Adam Roben.

        Copy PluginPackageWin.cpp to shared PluginPackage.cpp.
        Add PluginPackage.cpp to build configurations.
        Remove PluginPackage destructor from TemporaryLinkStubs.cpp.
        Use cross-platform pathGetFilename method.
        Remove platform-specific code from shared PluginPackage implementation.
        Remove shared code from PluginPackageWin.cpp.

        * GNUmakefile.am:
        * WebCore.pro:
        * WebCoreSources.bkl:
        * WebCore.vcproj/WebCore.vcproj:
        * platform/gtk/TemporaryLinkStubs.cpp:
        * platform/qt/TemporaryLinkStubs.cpp:
        * platform/wx/TemporaryLinkStubs.cpp:
        * plugins/PluginPackage.cpp:
        * plugins/win/PluginPackageWin.cpp:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@30650 268f45cc-cd09-0410-ab3c-d52691b4dbfc