lib: frame: avoid casting char* to short*

This might end up violating alignment requirements, so memcpy the
variable through a short variable instead.  For most systems, this
will optimize into the same code anyways, and for the rest, we need
to do it this way to avoid unaligned accesses crashing.

URL: https://bugs.gentoo.org/558436

lib/frame.c

@@ -40,8 +40,9 @@
 static const char *pr_dlci(const char *ptr)
 {
     static char buf[12];
-
-    snprintf(buf, sizeof(buf), "%i", *(short *) ptr);
+    short i;
+    memcpy(&i, ptr, sizeof(i));
+    snprintf(buf, sizeof(buf), "%i", i);
     return (buf);
 }