refs: http://www.keil.com/support/man/docs/armcc/armcc_pge1358787051159.htm

Stdio fixes after review

See #11.

drop write macros in favor of IO objects + fmt::Write

closes #4
closes #5
closes #6
closes #7
closes #11

watch tail -> tail -f

note that it's possible to skip the separate log file.

closes #9

Add `exit` and `report_exception` syscalls.

add a macro to write to the host stderr

also fix `write_all` logic when the a single write doesn't write all the bytes

fix typo in hprintln!

needed to cargo publish