Re-add FreeBSD support.

dwm.c

@@ -2169,18 +2169,25 @@ getparentprocess(pid_t p)
 {
 	unsigned int v = 0;
 
-#ifdef __linux__
+#if defined(__linux__)
 	FILE *f;
 	char buf[256];
 	snprintf(buf, sizeof(buf) - 1, "/proc/%u/stat", (unsigned)p);
 
 	if (!(f = fopen(buf, "r")))
-		return 0;
+		return (pid_t)0;
 
-	fscanf(f, "%*u %*s %*c %u", &v);
+	if (fscanf(f, "%*u %*s %*c %u", (unsigned *)&v) != 1)
+        v = (pid_t)0;
 	fclose(f);
-#endif /* __linux__ */
+#elif defined(__FreeBSD__)
+    struct kinfo_proc *proc = kinfo_getproc(p);
+    if (!proc)
+        return (pid_t)0;
 
+    v = proc->ki_ppid;
+    free(proc);
+#endif
 	return (pid_t)v;
 }