64-bit time_t

Index: src/TimeseriesExporter.cpp
--- src/TimeseriesExporter.cpp.orig
+++ src/TimeseriesExporter.cpp
@@ -162,7 +162,7 @@ int TimeseriesExporter::line_protocol_write_line(lua_S
   if(n < 0 || n >= dst_line_len - cur_line_len) goto line_protocol_write_line_err; else cur_line_len += n;
 
   /* timestamp (in seconds, not nanoseconds) and a \n */
-  n = snprintf(dst_line + cur_line_len, dst_line_len - cur_line_len, " %lu\n", tstamp);
+  n = snprintf(dst_line + cur_line_len, dst_line_len - cur_line_len, " %llu\n", (long long)tstamp);
   if(n < 0 || n >= dst_line_len - cur_line_len) goto line_protocol_write_line_err; else cur_line_len += n;
 
   return cur_line_len;