Change time_t conversion operator to ToTime_t() function

fpdfsdk/include/fsdk_baseannot.h

Index: fpdfsdk/include/fsdk_baseannot.h
diff --git a/fpdfsdk/include/fsdk_baseannot.h b/fpdfsdk/include/fsdk_baseannot.h
index 236e2c786888a06996bc90e146d818503db3106e..752d91a9039de8e94fec517aa933452cae0aeb0c 100644
--- a/fpdfsdk/include/fsdk_baseannot.h
+++ b/fpdfsdk/include/fsdk_baseannot.h
@@ -37,16 +37,12 @@ class CPDFSDK_DateTime {
   CPDFSDK_DateTime& operator=(const FX_SYSTEMTIME& st);
   bool operator==(const CPDFSDK_DateTime& datetime) const;
   bool operator!=(const CPDFSDK_DateTime& datetime) const;
-  bool operator>(const CPDFSDK_DateTime& datetime) const;
-  bool operator>=(const CPDFSDK_DateTime& datetime) const;
-  bool operator<(const CPDFSDK_DateTime& datetime) const;
-  bool operator<=(const CPDFSDK_DateTime& datetime) const;
-  operator time_t();
 
   CPDFSDK_DateTime& FromPDFDateTimeString(const CFX_ByteString& dtStr);
   CFX_ByteString ToCommonDateTimeString();
   CFX_ByteString ToPDFDateTimeString();
   void ToSystemTime(FX_SYSTEMTIME& st);
+  time_t ToTime_t() const;
   CPDFSDK_DateTime ToGMT() const;
   CPDFSDK_DateTime& AddDays(short days);
   CPDFSDK_DateTime& AddSeconds(int seconds);