The most important change for windows users is the replacement of the msys
tools by using busybox. This avoids the (harmless) "could not find /tmp
directory" messages.

All users will benefit from the reduced code size of the compiled binaries.
This results partly from the improved sdcc compiler efficiency and partly
from code improvements within the sduino library components.

- reduced binary size by splitting some Arduino core files
- reduced binary size by optimizing the pinMode() implementation
- using busybox as command shell for windows to run the wrapper scripts
- move the SPL compilation scripts into a separate project spl-splitter
- update SPL files to v2.3.0 (add support for STM8S001)
- flatten the repository structure
- update stm8gal to version 1.3.0
- updated SDCC to version 3.9/build 11242

- make sure main.c is pulled in for IDE builds as well
- building the core library when using make (regression bug in 0.4.0)

… domain (fix tenbaht#87)

…e transfer to the new owner

Now most tests can be compiled again. Some are too old to compile with the
current state of sduino, they are marked by an empty file NON-FUNCTIONAL.
Later, they might be either removed or adopted.