update jffs2, CYGPKG_FS_JFFS2_RET_DIRENT_DTYPE can be disable in jffs2_config.h; modify semaphore.h so that rt_mutex_init and work correctly in jffs2; fix a memory leak bug in dfs_jffs2.c when close directory

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1991 bbd45198-f89e-11dd-88c7-29a3b14d5316