Changes in trunk

[Richard Frith-Macdonald]

My latest commit to the base library in svn trunk hides some private  
internals of the memory management system, and this unfortunately  
means that code built with an older version will fail to link with an  
'undefined reference' error.

The solution is to rebuild all your code where any source file  
includes/imports NSZone.h

Sorry for any inconvenience.