Fix vararg type checking to accept ints for %c.

It's perfectly legitimate to format int values as %c, so don't assert in
this case.

Fixes #12192.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64798 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/strings/vararg.cpp

@@ -215,4 +215,8 @@ void VarArgTestCase::ArgsValidation()
     VarArgTestCase& somePOD = *this;
     WX_ASSERT_FAILS_WITH_ASSERT( wxString::Format("%s", somePOD) );
 #endif
+
+    // %c should accept integers too
+    wxString::Format("%c", 80);
+    wxString::Format("%c", wxChar(80) + wxChar(1));
 }