Merge pull request #10 from hadleyrich/master

Add toolchain location to Makefile
Merge pull request #11 from hadleyrich/master

Add global.h to usart.h and rename sysclk_millis to sysclk_ticks
Closes #7
Merge pull request #13 from hadleyrich/master

Add USART passthrough example. (Thanks Hadley!)
Fixed rename of sysclk_millis() to sysclk_ticks() missing from header.
Change TOOLBASE so it can be passed on command line
Enable interrupts when calling sysclk_init();
This should really be a different function, fixme!
Add ovf/comp hook handling.
Closes #1
Add an example using timers!
Backport changes to example Makefiles, can pass PORT or TOOLBASE on make command.
Remove usage of bool_t, it just fights with C++ and isn't that useful.
Purge bool_t no longer needed.
Adjust for changes to usart.h API
Add Timer PWM example, fading LEDs!
A better explanation of what timer-pwm.c is doing.
Maybe some useful comments on this example too?
Add a basic hello-world usart exmaple
Fix up init problem in usart_run().
Add support for passing MCU to compile against
Add support for different MCU to complile against