Upgrade ASM to 5.0.2

Change log: http://asm.ow2.org/history.html
 - Support for Java 8 annotations (on types and method parameters)
 - Fixes for stack map frames generation, maxLocals calculation

The initial commit in this PR resets all our customizations and is just a 1:1 copy of the asm
source tree. This simplifies future upgrades, see README.

The build will fail for all the intermediate commits. I can squash them to generate fewer failures,
but I think it would be good to keep at least those with [asm-cherry-pick].