Display AVR Memory Usage during make.

In order to see the resulting memory usage of our project display
it during make run. This heavily depends on the "--mcu" parameter
therefore take care of setting the value in "Makefile.inc" to
the one matching your processor.

output example:
___ [SIZE] _____________________________________________
avr-size -C --mcu=atmega328p main.out
AVR Memory Usage
----------------
Device: atmega328p

Program:    1652 bytes (5.0% Full)
(.text + .data + .bootloader)

Data:         14 bytes (0.7% Full)
(.data + .bss + .noinit)

___ [SIZE] _____________________________________________