gprs/gb_proxy: Use RAND_bytes for gbproxy TLLI/TMSI allocation

This change has some implications for the test case. It manipulated
bss_ptmsi_state and sgsn_tlli_state variables to make the output of
rand_r() and thus the TLLI/TMSI used predictable.
This possibility is gone when using RAND_bytes() so instead it is
overridden by a function that returns a deterministic sequence of values
(0x00dead00, 0x00dead01, ...). The test cases are adapted to expect
these values instead of the pseudo random values before.

The gbproxy_test stdout file changes as well, but only where the
TLLI/TMSI is displayed (in the hex dumps as well as the TLLI cache
entries).  All other output is the same.
diff --git a/openbsc/src/gprs/Makefile.am b/openbsc/src/gprs/Makefile.am
index dcc6842..f012003 100644
--- a/openbsc/src/gprs/Makefile.am
+++ b/openbsc/src/gprs/Makefile.am
@@ -2,7 +2,7 @@
 AM_CFLAGS=-Wall -fno-strict-aliasing $(LIBOSMOCORE_CFLAGS) \
 	$(LIBOSMOGSM_CFLAGS) $(LIBOSMOVTY_CFLAGS) $(LIBOSMOCTRL_CFLAGS) \
 	$(LIBOSMOABIS_CFLAGS) $(LIBOSMOGB_CFLAGS) $(COVERAGE_CFLAGS) \
-	$(LIBCARES_CFLAGS)
+	$(LIBCARES_CFLAGS) $(LIBCRYPTO_CFLAGS)
 OSMO_LIBS = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS) $(LIBOSMOVTY_LIBS) \
 	    $(LIBOSMOCTRL_LIBS) $(LIBOSMOGB_LIBS)
 
@@ -20,7 +20,7 @@
 			gb_proxy_patch.c gb_proxy_tlli.c gb_proxy_peer.c \
 			gprs_gb_parse.c gprs_llc_parse.c crc24.c gprs_utils.c
 osmo_gbproxy_LDADD = 	$(top_builddir)/src/libcommon/libcommon.a \
-			$(OSMO_LIBS) -lrt
+			$(OSMO_LIBS) $(LIBCRYPTO_LIBS) -lrt
 
 osmo_sgsn_SOURCES =	gprs_gmm.c gprs_sgsn.c gprs_sndcp.c gprs_sndcp_vty.c \
 			sgsn_main.c sgsn_vty.c sgsn_libgtp.c \