Changing submatching syntax from "->" to ":"  and M, MA to be shorthand for ($m:_M):1 and ($m:_M):2, respectively.
Also, "M" is optional if followed by ":", "M:1" is same as ":1"

Also, adding M in grammar to be shorthand for $m:_M (vargetter) op in match context.

fix crashes in markmatch / unmarkmatch caused by taking a reference to a shared pointer instead of just making a copy, and a typo