6419370: 4/4 new jmethodID code has tiny holes in synchronization
Summary: Fix races in jmethodID cache and JNI itable index cache.
Reviewed-by: ikrylov, acorn
6873059: Explicitly use -source 6 -target 6 when compiling with the boot jdk
Summary: The build fails if the bootstrap JDK defaults to <1.5
Reviewed-by: jcoomes