debian: Split libosmocore into various libs and address lintian warnings

Package the various libraries separately. This will allow to install
libosmogsm3 and libosmogsm4 in parallel.

E: libosmocore-dev: non-empty-dependency_libs-in-la-file usr/lib/libosmocore.la
E: libosmocore-dev: non-empty-dependency_libs-in-la-file usr/lib/libosmogb.la
E: libosmocore-dev: non-empty-dependency_libs-in-la-file usr/lib/libosmogsm.la
E: libosmocore-dev: non-empty-dependency_libs-in-la-file usr/lib/libosmovty.la

W: libosmocore-dbg: wrong-bug-number-in-closes l54:#nnnn
W: libosmocore: wrong-bug-number-in-closes l54:#nnnn

W: libosmocore: package-name-doesnt-match-sonames libosmocodec0 libosmocore4 libosmogb2 libosmogsm4 libosmovty0
diff --git a/debian/libosmocore-dev.install b/debian/libosmocore-dev.install
index eec0e15..ece5b08 100644
--- a/debian/libosmocore-dev.install
+++ b/debian/libosmocore-dev.install
@@ -3,3 +3,4 @@
 usr/lib/lib*.so
 usr/lib/lib*.la
 usr/lib/pkgconfig/*
+usr/share/doc/libosmocore/*