Allows classes extending ClassReader to decide if visit MethodParameters

With !278 (merged) MethodParameters attribute is skipped when using SKIP_DEBUG. That's stopping us from upgrading to a newer ASM version.

Having the decision being made in a protected method we could override it and start using a new version of ASM.

For clarity, not using the SKIP_DEBUG flag would not work for our case as that would include too much of extra things. Having a customizable condition for MethodParameters was the cleanest change I could came up with.