Compilation fix for wxUSE_STL==1 build after r67356.

An explicit conversion to char* is required in wxUSE_STL build.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67360 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/colourcmn.cpp

@@ -128,7 +128,7 @@ bool wxColourBase::FromString(const wxString& str)
             // passed as first argument: if it is a wide string, then %c
             // expects "wchar_t *" matching parameter under MSW for example.
             if ( sscanf(str.c_str() + 4,
-                        formatStr,
+                        formatStr.mb_str(),
                         &red, &green, &blue, alphaPtr) != 4 )
                 return false;