add P1.18, P1.20, P1.21, P1.23 as laser PWM pins
update config
Added P1.24, P1.26, P3.25, and P3.26 to Laser
Added P1.24, P1.26, P3.25, P3.26 to Laser config
Merge pull request #545 from Smoothieware/add/P1.23-to-laser-pwm

Add/p1.23 to laser pwm