working with exec_async

[voron00]

GetEntByNum() is one of those functions with a developer flag, they only work in a /# ... #/ comments like:

		/# 
    entity = clientNumToEntity( int(result[0]));
    if(result[1]=="OK"){
        entity iprintln("OK");
#/ 
	

Compiler will ignore everything under /# ... #/ comments unless developer_script is set to 1.

There is no performance impact on calling exec_async_checkdone every frame, well you can call it
not per frame maybe every 0.1 or something but you're gonna end up with slightly delayed callbacks then.