[M] Change in libosmocore[master]: util: add osmo_strbuf macros to manipulate the strbuf tail

Attention is currently required from: laforge, osmith.

neels has posted comments on this change. ( https://gerrit.osmocom.org/c/libosmocore/+/35207?usp=email )

Change subject: util: add osmo_strbuf macros to manipulate the strbuf tail ......................................................................

Patch Set 1:

(1 comment)

File include/osmocom/core/utils.h:

https://gerrit.osmocom.org/c/libosmocore/+/35207/comment/72c04f8d_08e8abc0 PS1, Line 329: } while (0)

(not related to here, macros are cool to get the actual source line/file indicated in logging, and f […]

I added real functions for the implementation, making them much more readable as a side effect, but i also kept the macros so the OSMO_STRBUF(sb, ...) pattern remains consistent in osmo_strbuf usage.