synchronize updateStringCache on mAccessLock

Resources.java used to synchronize on mTmpValue but has since
switched to mAccessLock. mTmpValue can be null in some instances
causing a NPE during a theme change.

Change-Id: I7411dfdf6e8e411381ae993872a3c740dad19300
Themes: Check CRC of APK MANIFEST.MF at install

Change-Id: I6ccfcd2b04107b85fe14cb678aad63443284353a