Add _c versions of functions that otherwise return static buffers

We have a habit of returning static buffers from some functions,
particularly when generating some kind of string values.  This is
convenient in terms of memory management, but it comes at the expense
of not being thread-safe, and not allowing for two calls of the
related function within one printf() statement.

Let's introduce _c suffix versions of those functions where the
caller passes in a talloc context from which the output buffer shall
be allocated.

Change-Id: I8481c19b68ff67cfa22abb93c405ebcfcb0ab19b
diff --git a/src/gb/gprs_ns.c b/src/gb/gprs_ns.c
index fc120ce..d72003e 100644
--- a/src/gb/gprs_ns.c
+++ b/src/gb/gprs_ns.c
@@ -1552,6 +1552,14 @@
 	return gprs_ns_ll_str_buf(buf, sizeof(buf), nsvc);
 }
 
+char *gprs_ns_ll_str_c(const void *ctx, const struct gprs_nsvc *nsvc)
+{
+	char *buf = talloc_size(ctx, INET6_ADDRSTRLEN+10);
+	if (!buf)
+		return buf;
+	return gprs_ns_ll_str_buf(buf, INET6_ADDRSTRLEN+10, nsvc);
+}
+
 void gprs_ns_ll_copy(struct gprs_nsvc *nsvc, struct gprs_nsvc *other)
 {
 	nsvc->ll = other->ll;