Checking file existence through VFS (potentially faster)

 The previous version was showing up in the profiler
Optimization: do not read data from input streams, use contents cached in VFS
Test that built-in binaries are up to date
Mutable field made volatile
getOriginal() pulled up
name and containingDeclaration pulled up
Javac target JVM version explicitly specified

When compiling from command line on a machine with Java 7 installed you get class format errors when running on Java 6 later