Modified README.md

* Added description of how to install the Cross Toolchain.
gpiomod_outptimer.c whitespace cleanup.
Changed comment style of gpiomod_outptimer.c from C99 to C89.
New file fix_print.sh for changing printk to pr_x.
Global printk fixing.

* Changed printk to pr_x in all .c files.
Fixed file name of fix_printk.sh.
Just some changes to the coding style.