Proposed change: weak symbol support for Darwin

[Andrew Pinski]

> How come nobody has complained about the fact that the Darwin compiler 
> has a badly broken C++ implementation?  My guess is it's because most 
> people don't use the Darwin compiler for C++; they use the Apple OS X 
> compiler instead, which is based on the GNU Darwin compiler but which 
> also includes Apple's local patches.  You see, the Darwin linker does 
> provide this functionality.  It's not quite the same as GNU linkonce 
> sections, but it's close enough; Apple calls it coalescing.

Someone has complained, see PR 11026 <http://gcc.gnu.org/PR11026>.
In fact someone at apple complained too, PR11384, 
<http://gcc.gnu.org/PR11384>.
Just since AIX, and other targets, have the same issue and there is an 
FAQ about
this problem some where no one has complained that much.

Thanks,
Andrew Pinski