reduce compiled size of drawChar
reduce compiled size of drawChar

- use a simple loop rather than linking in fillRect
- 208 bytes savings (sketch not using drawRect)

I didn't time it but this is quite likely faster as well since it
doesn't have the overhead of a stack of function calls resulting in tons
of jumps and push/pops to/from the stack.

yyyc514/ArduboyLib,davidperrenoud/Arduboy,Arduboy/Arduboy,davidperrenoud/Arduboy,yyyc514/ArduboyLib,Arduboy/Arduboy