Sometimes boards/*/Makefile.include (e. g. in case of the msba2) gets included
twice somehow, leading the TERMFLAG to be set twice and faulty. This
fixes that.
Many modules have subdirectories. Often these subdirectories should only
be included under certain circumstances. Modules that use submodules
currently need to use this pattern:
```make
DIRS = …
all: $(BINDIR)$(MODULE).a
@for i in $(DIRS) ; do $(MAKE) -C $$i ; done ;
include $(RIOTBASE)/Makefile.base
clean::
@for i in $(DIRS) ; do $(MAKE) -C $$i clean ; done ;
```
This PR moves the `all:` and `clean::` boilerplate into `Makefile.base`.
- switched to flashing using the programming port
- fixed Makefile.include
- fixes some documentation
- removed newlib nano.specs
- added OSX flashing support
- fixed flasher and port for OSX
- fixed port on OSX
- fixed bossac linux tool
- added license header