[Patch] Fix libstdc++/11378 (take2) + xsputn optmizations

[Jerry Quinn]

Paolo Carlini writes:
 > diff -urN libstdc++-v3-orig/include/std/std_fstream.h libstdc++-v3/include/std/std_fstream.h
 > --- libstdc++-v3-orig/include/std/std_fstream.h	2003-07-06 13:03:53.000000000 +0200
 > +++ libstdc++-v3/include/std/std_fstream.h	2003-07-06 18:48:02.000000000 +0200
 > @@ -365,7 +365,7 @@
 >  	// NB: _M_file.sync() will be called within.
 >  	if (this->pbase() < this->pptr())
 >  	  {
 > -	    int_type __tmp = this->overflow();
 > +	    const int_type __tmp = this->overflow();
 >  	    if (traits_type::eq_int_type(__tmp, traits_type::eof()))
 >  	      __ret = -1;
 >  	    else

Why this chunk?  It seems pointless.

Jerry