[Patch/mingw32] Don't depend on MS runtime for classic ctype table.\

[Paolo Carlini]

Hi,

>However, I think a better fix would be construct a generic static const
>ctype_base::mask _S_classic_table[256] in
>config/os/generic/ctype_noninline.h and just let mingw32 use the generic
>code.  I note that newlib (maybe others) has similar problem to mingw32,
>but it is not exposed because newlib doesn't define _GLIBCXX_USE_WCHAR_T
>  
>
did you analyze already which is the impact of these changes on binary 
compatibility? I suspect there may be problems, in particular when 
linking together objects pre and post changes (besides the symbols 
exported by the binary library itself)

In the light of those concerns, I think it's better for now to restrict 
the fixes to the mingw32 config, over which you have complete 
jurisdiction, and maybe reconsider the whole issue later, maybe fluently 
when we decide to break binary compatibility generally.

Paolo.