[LyX/master] Squash gcc warning.

[Pavel Sanda]

commit 0f8a2d2860c86c859064546876b2c99992dfd50d
Author: Pavel Sanda <sa...@lyx.org>
Date:   Thu Mar 27 01:10:59 2014 -0700

    Squash gcc warning.
    
    http://www.mail-archive.com/lyx-devel@lists.lyx.org/msg183142.html

diff --git a/src/support/filetools.cpp b/src/support/filetools.cpp
index 0012481..92aeaf7 100644
--- a/src/support/filetools.cpp
+++ b/src/support/filetools.cpp
@@ -1080,8 +1080,9 @@ int fileLock(const char * lock_file)
 void fileUnlock(int fd, const char * /* lock_file*/)
 {
 #if defined(HAVE_LOCKF)
-       if ( fd >= 0) {
-               (void) lockf(fd, F_ULOCK, 0);
+       if (fd >= 0) {
+               if (lockf(fd, F_ULOCK, 0))
+                       LYXERR0("Can't unlock the file.");
                close(fd);
        }
 #endif