Fix building of layer23 against in-tree libosmocore

[Harald Welte]

Hi all!

As Andreas has pointed out to me in a phone call yesterday and steve-m
mentioned on IRC:  Building layer23 with the not-installed (make
install) libosmocore from osmocom-bb resulted in link failures.

I've now addressed those problems and the repo should be building just
fine again.

Regards,
	Harald.
-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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