Compile time warnings

Some compile time warnings occurred. Solutions have been added for these cases, somewhat categorized. 
I looked at the implementation of this method on the base class, and it appears to have the same implementation with ASM5 (which is what we're using. I'm not sure why we need to SuppressWarnings though, we don't call it anywhere? We should be safe to remove this Override though.

http://websvn.ow2.org/filedetails.php?repname=asm&path=%2Ftags%2FASM_5_0_3%2Fsrc%2Forg%2Fobjectweb%2Fasm%2FMethodVisitor.java