[OML] parse attributes depending on BTS type

Some NM attributes are defined differently depending on
the BTS type.  Having one big nm_att_tlvdef[] table for
all BTS types is no longer sufficient.  This patch

* introduces 'struct gsm_bts_model' to describe a BTS model
* adds definitions of gsm_bts_model for BS-11 and nanoBTS
* changes the abis_nm_tlv_parse() function: include a bts pointer
diff --git a/openbsc/src/Makefile.am b/openbsc/src/Makefile.am
index 7d7fee7..aa50b8c 100644
--- a/openbsc/src/Makefile.am
+++ b/openbsc/src/Makefile.am
@@ -12,7 +12,7 @@
 		trau_frame.c trau_mux.c paging.c e1_config.c e1_input.c tlv_parser.c \
 		input/misdn.c input/ipaccess.c signal.c gsm_utils.c talloc.c \
 		talloc_ctx.c system_information.c bitvec.c rest_octets.c \
-		rtp_proxy.c statistics.c
+		rtp_proxy.c statistics.c bts_siemens_bs11.c bts_ipaccess_nanobts.c
 
 libmsc_a_SOURCES = gsm_subscriber.c db.c telnet_interface.c \
 		mncc.c gsm_04_08.c gsm_04_11.c transaction.c \
@@ -27,7 +27,8 @@
 bsc_hack_LDADD = libmsc.a libbsc.a libmsc.a libvty.a -ldl -ldbi $(LIBCRYPT)
 
 bs11_config_SOURCES = bs11_config.c abis_nm.c gsm_data.c msgb.c debug.c \
-		      select.c timer.c rs232.c tlv_parser.c signal.c talloc.c
+		      select.c timer.c rs232.c tlv_parser.c signal.c talloc.c \
+		      bts_siemens_bs11.c
 
 ipaccess_find_SOURCES = ipaccess/ipaccess-find.c select.c timer.c