optimised INCR & DECR variable

[LCD]

Because I also coded some stuff in AMOS on Amiga: How about optimised INCR and DECR commands for variables? This can be easyly optimised because Z80 knows INC and DEC commands, and variable=variable+1 is maybe much slower.
INCR variable incrases the value by one. This will be very handy, I think .