bug#1578: emacsclient -c make emacs very slow (under Mac OSX)

[Adrian Robert]

> First, I use emacs -nw to open a normal emacs in the terminal.  Then I
> use emacsclient -c to open a carbon frame.  Now the terminal emacs
> becomes very slow and unresponsive. (But the CPU is not running high).
> Even after the carbon frame is closed, it is still same slow. (and I
> have to close emacs and restart)

This is because the events are being passed only after a full run  
through the NS event loop.  See line 3194 in nsterm.m (the first one  
of ns_select()).  Ideally this would drop down to the regular select 
() if the NS application ("carbon" frame) is not active.  However, I  
haven't found a way to detect this without also causing the problem  
of failing to pick up the app becoming active again until after a  
long delay.  I think the select() gets called with a long timeout  
and, no matter if cocoa-experimental-ctrl-g is set or not, no  
interruption of it happens.

Since there is only one thread, an external call to, e.g. - 
applicationWillBecomeActive won't go through until after this select  
terminates.