src/msgb.c: print an error if msgb allocation failed

Printing an error message when msgb allocation failed was initially
intended, but have been commented out for years. This would
facilitate the bug hunting process, especially on embedded
platforms with limited resources (e.g. amount of RAM).

The GLOBAL logging subsystem with FATAL level is used
for printing such messages.

Change-Id: I3e2d1beabd6936fc28a1ad664c083ff1698bb644
diff --git a/src/msgb.c b/src/msgb.c
index 9efaea5..82902b4 100644
--- a/src/msgb.c
+++ b/src/msgb.c
@@ -62,6 +62,7 @@
 
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/talloc.h>
+#include <osmocom/core/logging.h>
 
 void *tall_msgb_ctx = NULL;
 
@@ -81,7 +82,8 @@
 	msg = _talloc_zero(tall_msgb_ctx, sizeof(*msg) + size, name);
 
 	if (!msg) {
-		//LOGP(DRSL, LOGL_FATAL, "unable to allocate msgb\n");
+		LOGP(DLGLOBAL, LOGL_FATAL, "Unable to allocate a msgb: "
+			"name='%s', size=%u\n", name, size);
 		return NULL;
 	}