Perform localized comparison via wstring

On OS X and Windows the existing solution for localized comparison seems
to be struggling.  Try performing the comparison on std::wstring
rather than string, which should sidestep any character encoding issues.

src/translations.cpp

@@ -695,6 +695,11 @@ std::string operator+( const translation &lhs, const translation &rhs )
 }
 
 bool localized_comparator::operator()( const std::string &l, const std::string &r ) const
+{
+    return ( *this )( utf8_to_wstr( l ), utf8_to_wstr( r ) );
+}
+
+bool localized_comparator::operator()( const std::wstring &l, const std::wstring &r ) const
 {
     return std::locale()( l, r );
 }

src/translations.h

@@ -269,6 +269,7 @@ struct localized_comparator {
     }
 
     bool operator()( const std::string &, const std::string & ) const;
+    bool operator()( const std::wstring &, const std::wstring & ) const;
 };
 
 constexpr localized_comparator localized_compare{};