Remove unnecessary c_str() from wx var arg functions arguments

Using c_str() for arguments to wxString::Printf(), Format() and
wxLogXXX() is useless since wx 2.9 days, so simply remove them.

No real changes, this is just a (long due) cleanup.

src/msw/iniconf.cpp

@@ -452,7 +452,7 @@ bool wxIniConfig::DeleteAll()
   strFile << '\\' << m_strLocalFilename;
 
   if ( wxFile::Exists(strFile) && !wxRemoveFile(strFile) ) {
-    wxLogSysError(_("Can't delete the INI file '%s'"), strFile.c_str());
+    wxLogSysError(_("Can't delete the INI file '%s'"), strFile);
     return false;
   }