(svn r21435) -Fix: NewGRF strings that referenced a value that was set by a string command later in the string failed

src/newgrf_text.h

@@ -39,6 +39,9 @@ void StopTextRefStackUsage();
 void SwitchToNormalRefStack();
 void SwitchToErrorRefStack();
 void RewindTextRefStack();
+bool UsingNewGRFTextStack();
+struct TextRefStack *CreateTextRefStackBackup();
+void RestoreTextRefStackBackup(struct TextRefStack *backup);
 uint RemapNewGRFStringControlCode(uint scc, char *buf_start, char **buff, const char **str, int64 *argv);
 
 StringID TTDPStringIDToOTTDStringIDMapping(StringID string);