add classloader support to classweaver

My project does a lot of java code generation that is then weaved by the weaver.  This is all done in memory, no file system interaction at all.  We directly use the ClassWeaver rather than Tools/Weaver.  We also utilise a custom classloader to provide dynamic resolution of dependencies that might have also been generated previously.

With the updates to use asm 4.1 our code stopped working.  I managed to get everything working again by adding support for classloader in asm ClassWriter.

I got this exact error in my code when upgrading to the stackmap branch of kilim.

http://stackoverflow.com/questions/11292701/error-while-instrumenting-class-files-asm-classwriter-getcommonsuperclass