Updated core-lib

Signed-off-by: Stefan Marr <git@stefan-marr.de>
Merge ..//RPySOM
promote the stackpointer

this is a good idea because the stack depth is always the same at the
same bytecode position
_previous_frame is not immutable

(clear_previous_frame writes it)
don't store _local_offset

retrieving it from the method is fine
pass along the frame and method to the bytecodes

the JIT cannot track what happens to the method and frame if they are
stored on the interpreter, just pass them along. (code looks nicer too.)
when actually reading the method, promote it

(it's green anyway, so it doesn't cost anything at all)