OML: Improve OML attribute handling

the OML attribute tables are hardcoded. To set variable parameters,
the hardcoded data structure (tlv) is patched on byte level during
runtime. This patch replaces this mechanism.

- Replace hardcoded OML attribute tables with dynamically
  generated TLV structures.

- Add unit tests to check if the OML attribute tables are
  generated correctly

- Put OML attribute table generator code in a separate file:
  bts_ipaccess_nanobts_omlattr.c

Change-Id: Ibeb34a84912d6cf695f553a34c69320fca7d08fa
diff --git a/openbsc/src/libbsc/Makefile.am b/openbsc/src/libbsc/Makefile.am
index 4728e23..8c53817 100644
--- a/openbsc/src/libbsc/Makefile.am
+++ b/openbsc/src/libbsc/Makefile.am
@@ -49,5 +49,6 @@
 	bsc_ctrl_lookup.c \
 	net_init.c \
 	bsc_dyn_ts.c \
+	bts_ipaccess_nanobts_omlattr.c \
 	$(NULL)