Add PWM device type
Add IFX CCU4 pwm driver
Add PWM example.
Add some GPIO Macros and use them in i2c uart and pwm drivers.
Merge branch 'feat/dev/gpio' into develop
Add stubs.c module.
Add _sbrk alias to sbrk
Increase stack size(just in  case...)
Add some file related syscall for newlib
Update init.S
Use printf function in place of dev_write.
Update makefiles
Use smaller iprintf.
Cosmetic change in task_struct.
Update impure_ptr after task switch.
Reduce stack size to fit.
Update Makefile and linker_script
Update README
Change newlib path
Increase heap size.
http://osdir.com/ml/lib.newlib/2007-09/msg00012.html
Don't use reent struct yet.
TODO: Implement per task reent struct in a correct way.