Add macros for diagnostic control, use them in locale/weightwc.h

[Joseph Myers]

On Tue, 25 Nov 2014, Paul Eggert wrote:

> Joseph Myers wrote:
> > It's only in a particular bit of code where we want to assume it's
> > initialized.
> 
> We could use ASSUME_INITIALIZED only in the particular bit of code where it's
> needed, as it doesn't have to be used immediately after a declaration.

But won't the proposed asm, with its output operand for resplen, imply 
that any previous value in resplen is dead - which is not correct if you 
use it only there (where the point is that in fact there is a value there, 
which is not dead, but the compiler can't see there must be a value there) 
rather than before any possible initialization?

-- 
Joseph S. Myers
joseph@codesourcery.com