Include wchar.h so that mbstate_t is available in global namespace. Maybe,

I should revert the last patch, which made the file use ::mbstate_t as
opposed to std::mbstate_t, but I'm waiting for Pavel to tell why it was
necessary to use ::mbstate_t and if this version of borland can be made
to work in some other way.


[SVN r23528]

include/boost/program_options/detail/utf8_codecvt_facet.hpp

@@ -48,6 +48,8 @@
 // specialized on those types for this to work.
 
 #include <locale>
+// for mbstate_t
+#include <wchar.h>
 
 #include <boost/program_options/config.hpp>