#3 Freestanding configurations

[Liviu Ionescu (ilg)]

In the new version, projects created as 'freestanding' are assumed to really run without any POSIX support; to enforce this, we no longer include the empty definitions of all posix calls.

Unfortunately some newlib calls are not designed to work in true freestanding configurations, and, in some error cases, call various other functions, for example abort().

To compensate for this, I added a custom version of abort() in the _exit.c file, and some empty definitions in _syscalls.c (raise() and kill).

I would appreciate intensive tests with the 'freestanding' configuration to identify if there are other functions required.