Reviewed by Darin.

        <rdar://problem/5772987> Crashing viewing page with two VLC plug-in
        instances

        The VLC Netscape plug-in crashes if more than one instance is created.

        Added a quirk that disallows a plug-in from having more than one
        instance and set this for the VLC plug-in.

        In addition, we now sort plug-ins that handle the same MIME
        type to choose the most appropriate one. This sorting first sorts by
        whether a plug-in has an issue that should put it at the end of the
        list, then whether it appears in a "preferred" plug-in directory.

        * plugins/PluginQuirkSet.h: Added PluginQuirkDontAllowMultipleInstances.
        * plugins/PluginDatabase.cpp:
        (WebCore::PluginDatabase::preferredPluginCompare): Comparator for
        sorting plug-ins; calls PluginPackage::compare().
        (WebCore::PluginDatabase::pluginForMIMEType): Add all of the plug-ins
        that handle this MIME type to a list, sort the list, and return the
        first item.
        (WebCore::PluginDatabase::MIMETypeForExtension): Add all of the plug-ins
        that handle this extension to a list, sort the list, and return the MIME
        type used by the plug-in at the beginning of the list.
        * plugins/PluginDatabase.h:
        * plugins/PluginPackage.h:
        (WebCore::PluginPackage::version): Added; returns the module version.
        * plugins/win/PluginDatabaseWin.cpp:
        (WebCore::PluginDatabase::isPreferredPluginPath): Made static; removed
        const.
        * plugins/win/PluginPackageWin.cpp:
        (WebCore::PluginPackage::compare): Sorts plug-ins with known issues to
        the end, then plug-ins in preferred directories to the beginning, then
        alphabetically by file name, numerically by version, and alphabetically
        by parent directory.
        (WebCore::PluginPackage::determineQuirks): Set the "don't allow multiple
        instances" quirk for VLC.
        (WebCore::PluginPackage::load): Return false if the plug-in library has
        already been loaded and the "don't allow multiple instances" quirk is
        set.
        * platform/gtk/TemporaryLinkStubs.cpp:
        (PluginPackage::compare): Added stub.
        (PluginDatabase::IsPreferredPluginPath): Update the GTK stub.
        * platform/qt/TemporaryLinkStubs.cpp:
        (PluginPackage::compare): Added stub.
        (PluginDatabase::IsPreferredPluginPath): Update the Qt stub.
        * platform/wx/TemporaryLinkStubs.cpp:
        (PluginPackage::compare): Added stub.
        (PluginDatabase::IsPreferredPluginPath): Update the wx stub.




git-svn-id: http://svn.webkit.org/repository/webkit/trunk@30698 268f45cc-cd09-0410-ab3c-d52691b4dbfc