libmsc: Use RAND_bytes when choosing a tmsi

Require openssl version to be >= 0.9.5 because we rely on the RAND_bytes
return value.

[hfreyther: Add cast to uint8_t*]
diff --git a/openbsc/src/libmsc/Makefile.am b/openbsc/src/libmsc/Makefile.am
index aa7d8ae..18bfa0c 100644
--- a/openbsc/src/libmsc/Makefile.am
+++ b/openbsc/src/libmsc/Makefile.am
@@ -1,6 +1,6 @@
 AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include -I$(top_builddir)
 AM_CFLAGS=-Wall $(LIBOSMOCORE_CFLAGS) $(LIBOSMOVTY_CFLAGS) \
-	$(LIBOSMOABIS_CFLAGS) $(COVERAGE_CFLAGS)
+	$(LIBOSMOABIS_CFLAGS) $(COVERAGE_CFLAGS) $(LIBCRYPTO_CFLAGS)
 
 noinst_HEADERS = meas_feed.h