PWM fixes, slow down fan update

include LPC1768 syntax for M42

couple more pin_t changes

consistency

change M42 to R, P format

Revert "change M42 to R, P format"

This reverts commit 01f12f579ec9ccc1bb9126e68d2c86449e9b7edf.

Marlin/src/gcode/control/M42.cpp

@@ -28,6 +28,11 @@
  * M42: Change pin status via GCode
  *
  *  P<pin>  Pin number (LED if omitted)
+ *            For LPC1768 use M42 P1.20 S255 if wanting to set P1_20 to logic 1
+ *              NOTE - Repetier Host truncates trailing zeros on a decimal when
+ *                     sending commands so typing M42 P1.20 S255 results in 
+ *                     M42 P1.2 S255 being sent.  Pronterface doesn't have this issue.
+ *                     
  *  S<byte> Pin status from 0 - 255
  */
 void GcodeSuite::M42() {