Target hook - compiler specific pragmas.

[Iain Buclaw]

As part of the front-end harmonising work I'm doing, will be 
adding in a Target hook to handle compiler-specific pragmas.  
This would abstract out code like this in LDC.

https://github.com/ldc-developers/ldc/blob/master/dmd2/attrib.c#L1113
https://github.com/ldc-developers/ldc/blob/master/dmd2/attrib.c#L1182

Which implements these pragmas.

http://wiki.dlang.org/LDC-specific_language_changes#Pragmas


I have plans for adding in pragmas into GDC at a later date too 
as I plan to make the magic modules of GDC re-locatable 
(core.stdc.stdarg, gcc.builtins, etc...)


David, you OK with this? :-)


Regards
Iain.