Fix for this bug:

	Radar 3128631 (WebFileDatabase walks its whole directory tree to expire files)

	Complete reworking of the way in which the disk cache database keeps track
	of the files on disk. This should result in fewer I/O operations, and
	should fix the extremely bad behavior that involved walking the entire
	disk cache tree evey time a single file needed to be deleted.

        * Database.subproj/WebFileDatabase.h: Use new WebLRUFileList code.
        * Database.subproj/WebFileDatabase.m: Ditto.
        * Database.subproj/WebLRUFileList.h: Added.
        * Database.subproj/WebLRUFileList.m: Ditto.
        * Misc.subproj/WebFoundationLogging.h: Added WebFoundationLogWebFileDatabaseActivity channel
        * Misc.subproj/WebFoundationLogging.m: Ditto
        * WebFoundation.pbproj/project.pbxproj: Added WebLRUFileList.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@3100 268f45cc-cd09-0410-ab3c-d52691b4dbfc