Update eeprom.c

Function eeprom_put_char's parameters did not align with the .h file.
Update gcode.c

home_select defined out of scope. Moved it outside the switch 
so the rest of the switch can see it properly. 
Update eeprom.c

Changed back
Update eeprom.h

Fixed the function signature.
Update gcode.c

Removed the home_select variable.
G-code updates for G10 L2 and L20

- Updated g-codes G10 L2 and G10 L20 to the new descriptions on
linuxcnc.org
Update README.md
Increased g-code parser line buffer. Added line overflow feedback.

- Increased g-code parser line buffer from 50 to 70 characters. Should
fix most all issues with long arc statements, provided that they are 8
digits(float) long only.

- Added a line buffer overflow feedback error to let the user know when
it encounters this problem. Resets the line whenever this occurs.
(Thanks @BHSPitMonkey!)
Updated readme
fix command line parameter for avr-size
Make serial work with most chips by default
Added pin mapping list to docs, useful for porting
Refactor config.h to allow defaults for chips/boards with different pin mappings
Processor-independent pin mapping feature.

- Cleaned up and organized pin mapping concept by @elmom.

- pin_map.h allows for user-supplied pin mapping and port vector
definitions in a centralized file. With more processor types, more
definitions could be added.
Pin map definition cleanup.
remove mcu argument for avr-size in makefile as it is not present in GNU Binutils 2.22