[libstdc++] Don't access fpos_t.__state on uClibc w/o wchar support

[Gabriel Dos Reis]

Pétur Runólfsson <peturr02@ru.is> writes:

| Gabriel Dos Reis wrote:
| >Why can't you use the standard idiom
| >
| >  #if _GLIBCXX_USE_WCHAR_T
| 
| This won't work because fpos<mbstate_t> is also used for narrow streams.

then we've get a design problem then. 

| The correct fix for this is to not implement fpos<> in terms of fpos_t,
| which is how things were until this checkin:
| 
| 2003-07-03  Benjamin Kosnik  <bkoz@redhat.com>

I'll let Benjamin to comment -- but there'll be some delay.

-- Gaby