Specified bit-widths for all integer types.
Added AVR compiler target to Makefile.
Added interfaces for compare output mode config.

Added simple set and get functions for setting compare output mode of a
timer. Also removed 'inline' descriptors from mock system functions, as
they unnecessary. Added blank test for checking for no timer start when
no period was set.
Refactored header file.

Cleaned up the header file and added more documentation for function
parameters. Also added a blank test case for cycle-time overflow
detection.