Constant Char "PA[]" collides with other libraries

I changed this a several other instances of the use of PA[] to ZPA[] which avoids collision with AVR128 Board Manager libraries. Please use larger variable names in the future to avoid collision with board managers.

Line 214: const char PA[] PROGMEM = "Pa"; 
Line 281: PA, 
Line 314: PA,

Not sure that's all of them. 