[LyX/master] Fix compilation warning in DepTable.cpp

[Jean-Marc Lasgouttes]

commit 167eea3990a1a2b5e64ab05ebb26986e76c3b160
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Mon Mar 20 15:03:09 2017 +0100

    Fix compilation warning in DepTable.cpp
---
 src/DepTable.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/DepTable.h b/src/DepTable.h
index 7f687cc..0d78ab8 100644
--- a/src/DepTable.h
+++ b/src/DepTable.h
@@ -58,7 +58,7 @@ private:
                /// Current CRC value - only re-computed if mtime has changed.
                unsigned long crc_cur;
                /// mtime from last time current CRC was calculated.
-               long mtime_cur;
+               std::time_t mtime_cur;
                ///
                bool changed() const;
        };