[RFC] Variants of __typeof

[Richard Henderson <rth at redhat dot com>]

While attempting to write some code that uses the new x86 named address space 
support in gcc 6, I found that __typeof is very unhelpful.  In particular, given

	int __seg_fs *ptr;
	__typeof(*ptr) obj;

OBJ will not be type "int", but "int __seg_fs".  Which means that you can't use 
it to create temporaries within statement expressions.

In the process of writing this, I found a hack in __typeof added just to 
support _Atomic.  Which suggests that one of these variants would be more 
generally helpful than the hack.

I add __typeof_noas and __typeof_noqual.  The first strips only the address 
space, leaving 'const' and 'volatile' (and, I suppose 'restrict').  The second 
strips all qualifiers, essentially yielding the TYPE_MAIN_VARIANT.

Thoughts?


r~

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