dist: travis: add gdb to travis

native: compile with -g, "make term" runs through gdb

doc: provide include path list for doxyfile

net ipv6: use full include path

Using an "absolute" instead of a relative include path, make the doxygen output less confusing.

cpu/kinetis_common: Add periph/dac implementation

pkg: unify git checkout

make: buildtest: pass GIT_CACHE_DIR to buildtest targets

gnrc: simplify hdr_build functions

gnrc_rpl: add netif_addr to DODAG

pba-d-01-kw2x: enable support to flash board selected by its SERIAL no

Directly using 16 bit port numbers instead of casting uint8_t pointers.

gnrc_rpl: new default route when old one was deleted

dist: compile_test.py: build everything on changes in pkg/