[COMMIT] Final PMC additions

concat, set, {add,sub,mul,div} implemented.
The following instructions will now work as in perl5...

set P0,3
set P1,"foo"
concat P0,P0,P1 # "3foo"
set P0,3
add P0,P0,P1 # 3
set P0,-13.3
set P1,"13.3"
add P0,P0,P1 # 0 (even though P1 is a string)

The code for add/sub/mul/div has to be able to be simplified somehow. It
passes the requisite tests so I'm calling it good for now, but there's
probably a very simple optimization that I'm missing at 1:30 A.M.

-Jeff
<jgoff@blackboard.com>

• [COMMIT] Final PMC additions by Jeff G
• Re: [COMMIT] Final PMC additions by Simon Cozens