(posix_fileno) [_WIN32]: Rename posix_fileno() to fileno().

Remove the extern posix_fileno().

(fileno) [_WIN32]: Replace system fileno() with a function that supports posix
file descriptors.  Move #undef fileno to w32misc.h as the system define
is in stdio.h.

(rea) [_WIN32]: Add stdio.h for fileno() extern declaration and add misc.h
to ensure the WIN32 fixes to stdio.h are included.

src/lib/w32/w32misc.h

@@ -46,6 +46,7 @@
 /* stdio.h */
 #define vsnprintf _vsnprintf
 #define snprintf _snprintf
+#undef fileno
 
 /* stdlib.h */
 #define random rand