Reviewed by Anders Carlsson.

        Bug 16779: Make the PluginStream implementation be shared across platforms
        http://bugs.webkit.org/show_bug.cgi?id=16779

        Add the new shared PluginStream files to the GTK+ and Win32 builds.
        Add PluginStreamClient class for the streamDidFinishLoading method.
        Add open/close/write methods to FileSystem for temporary file handling.
        Add PluginDebug.h and npfunctions.h for shared PluginStream.
        Add shared PluginStream.
        Remove PluginStreamWin.
        Update PluginViewWin to use shared PluginStream and PluginStreamClass.

        * GNUmakefile.am:
        * WebCore.pro:
        * WebCore.vcproj/WebCore.vcproj:
        * platform/FileSystem.h:
        * platform/gtk/FileSystemGtk.cpp:
        * platform/win/FileSystemWin.cpp:
        * plugins/PluginDebug.h:
        * plugins/PluginStream.cpp:
        * plugins/PluginStream.h:
        * plugins/npfunctions.h:
        * plugins/win/PluginDebug: Moved to PluginDebug.h.
        * plugins/win/PluginStreamWin.cpp: Moved to PluginStream.cpp.
        * plugins/win/PluginStreamWin.h: Moved to PluginStream.h
        * plugins/win/PluginViewWin.cpp:
        * plugins/win/PluginViewWin.h:
        * plugins/win/npfunctions.h: Moved to npfunctions.h


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@29399 268f45cc-cd09-0410-ab3c-d52691b4dbfc