The CAN stack support only raw CAN at this time.
It contains a device interface (drivers/include/can/candev.h) and the data link
layer, build around can/device.c can/pkt.c and can/router.c. can/dll.c contains
the upper level and lower level interface to send and receive CAN frames.
Upper layer interface is located in include/can/raw.h
The packet buffer was originally designed to have a replaceable
back-end. This is why the actual module is called `gnrc_pktbuf_static`.
However, since than some auxiliary functions snuck into the static
back-end, which should go into the common module (which is a
pseudo-module at the moment).
This fix makes the `gnrc_pktbuf` pseudo-module an actual module and
moves the auxiliary functions to that module.
- Copied the relevant parts of mipshal.mk from the toolchain
- Cleaned up CFLAGS and more in Makefile.include
- Added empty syscalls implementation which can be used to interface
with the UHI system
- Added a note on why -std=gnu99 is necessary for this CPU presently
