libmaa: enable on darwin

pkgs/servers/dict/libmaa.nix

···
   env.NIX_CFLAGS_COMPILE = "-Wno-error=format-truncation";
 
   meta = with lib; {
-    description = "Dict protocol server and client";
-    maintainers = [ ];
-    platforms = platforms.linux;
+    description = "Provides many low-level data structures which are helpful for writing compilers";
+    license = licenses.gpl2Plus;
+    maintainers = with maintainers; [ sikmir ];
+    platforms = platforms.unix;
   };
 }