Use of lsof to fix slam for specific mountpoint

Apparantly fuser didn't report back, if the tomb was mounted in a subdir of /run (whereas /run itself is often a tmpfs mount).
With no list of process ids those couldn't be killed, so slamming the tomb failed.
lsof is capable to report back the sought information.

Fixes #220

Additionally fixing the debug output, where a hardcoded mountpoint was used

INSTALL.md

@@ -9,6 +9,7 @@ Tomb needs a few programs to be installed on a system in order to work:
  * gnupg
  * cryptsetup
  * pinentry-curses (and/or -gtk-2, -x11, -qt)
+ * lsof
 
 Most systems provide these tools in their package collection, for
 instance on Debian/Ubuntu one can use `apt-get install` on Fedora and

tomb

@@ -2506,20 +2506,20 @@ umount_tomb() {
 # Kill all processes using the tomb
 slam_tomb() {
     # $1 = tomb mount point
-    if [[ -z `fuser -m "$1" 2>/dev/null` ]]; then
+    if [[ -z `lsof -t +D "$1" 2>/dev/null` ]]; then
         return 0
     fi
     #Note: shells are NOT killed by INT or TERM, but they are killed by HUP
     for s in TERM HUP KILL; do
         _verbose "Sending ::1:: to processes inside the tomb:" $s
         if option_is_set -D; then
-            ps -fp `fuser -m /media/a.tomb 2>/dev/null`|
+            ps -fp `lsof -t +D "$1" 2>/dev/null`|
             while read line; do
                 _verbose $line
             done
         fi
-        fuser -s -m "$1" -k -M -$s
-        if [[ -z `fuser -m "$1" 2>/dev/null` ]]; then
+        kill -$s `lsof -t +D "$1"`
+        if [[ -z `lsof -t +D "$1" 2>/dev/null` ]]; then
             return 0
         fi
         if ! option_is_set -f; then