logging.h: fixup: shorter names for LOGGING_FILTER_* and LOGGING_CTX_*

My recent logging patch was merged to master a bit too soon. Accomodate the
request for naming that matches the general "LOG" prefix instead of "LOGGING".

libosmocore will not be backwards-compatible with the few commits from
change-id I5c343630020f4b108099696fd96c2111614c8067 up to this one. This and
following commits are backwards compatible with those before that short window.

See also:
* openbsc change-id Ib2ec5e4884aa90f48051ee2f832af557aa525991
* osmo-pcu change-id I4db4a668f2be07f3d55f848d38d1b490d8a7a685

Change-Id: I424fe3f12ea620338902b2bb8230544bde3f1a93
8 files changed