Updates for automake 1.13

Hi, automake 1.13 appeared on my system lately. As with every version bump of auto* some directives are no more 'en vogue'. This time it's INCLUDES in Makefile.am files. AM_CPPFLAGS should be used now, INCLUDES will be removed in some future release. I created trivial patches for the osmo projects using autotools of which I already had clones. These are: libosmo-abis libosmocore libosmo-dsp libosmo-sccp openbsc osmo-bts osmocom-bb osmo-gmr The patches are for the master branch of the respective repository, current HEAD. I'll send the patches individually. Feel free to apply the patches if they seem useful. Otherwise, feedback is appreciated. Kind regards, -Alexander Huemer