engine: zone: add small allocation optimization, reducing the size of <255 bytes allocations at the cost of less debug info

Keep it opt-in through a flag at pool alloc time.
Opt-in console related allocations, they are usually small enough strings.

engine/common/cmd.c

@@ -1454,7 +1454,7 @@ Cmd_Init
 */
 void Cmd_Init( void )
 {
-	cmd_pool = Mem_AllocPool( "Console Commands" );
+	cmd_pool = Mem_AllocPoolExt( "Console Commands", MEM_SMALL_ALLOC_OPT );
 	cmd_functions = NULL;
 	cmd_condition = 0;
 	cmd_wait = 0;