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/configure.ac b/openbsc/configure.ac
index e2575c1..b18ecc1 100644
--- a/openbsc/configure.ac
+++ b/openbsc/configure.ac
@@ -244,6 +244,7 @@
     tests/sndcp_xid/Makefile
     tests/slhc/Makefile
     tests/v42bis/Makefile
+    tests/nanobts_omlattr/Makefile
     doc/Makefile
     doc/examples/Makefile
     Makefile)