Most of other [lib]osmo-projects do include these files in the release
tarballs. Do the same for the sake of consistency.
Change-Id: I5c15cefb68ab787819edaa1a097fe397837e0bcd
Related: OS#6227
Since automake 1.13 INCLUDES is depricates and causes a warning
Inspired from similar patches by Alexander Huemer for other osmocom
projects
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>