[patch ada]: Fix issues about multilib build of native windows

[Arnaud Charlet]

> Split submitted patch from thread "[patch ada]: Fix issues about
> multilib build of native windows and handle MSG_WAITALL for windows
> native targets"
> into separate ones.
> 
> ChangeLog gcc/ada (ada_w_multi.txt)
> 
> 2011-03-28  Kai Tietz
> 
> 	* gcc-interface/Makefile.in (SO_LIB): Handle multilib build for native
> 	windows targets.
> 	(EH_MECHANISM): Make sure we use gcc's exception mechanism for all
> 	native windows target.
> 	* system-mingw.ads (System): Change ZCX_By_Default default to
> 	True.

OK, thanks.