[v3 PATCH]: Fix bootstrap failure on powerpc-apple-darwin7.9.0

[Paolo Carlini]

Roger Sayle wrote:

>The following simple patch fixes the current bootstrap failure on
>powerpc-apple-darwin7.9.0.  This issue is that the darwin system
>headers define the macro "_T", so this identifier can't be used.
>The workaround is to simply rename the problematic use of "_T" in
>include/ext/codevt_specializations.h's __iconv_adaptor.
>
>Tested on powerpc-apple-darwin7.9.0 where a bootstrap now progresses
>past the current failure.  Ok for mainline?
>  
>
Could you please test _Tp instead, more consistent with the rest of the 
library? Pre-approved of course.

Thanks,
Paolo.