Added new subcommand for debugvm

VBoxManage removed "debug" from list of commands in help, leaving only
description for "debugvm" in section "Introspection and guest debugging"
below all of the list, so that it is needed for adding "debugvm" to the
list of available commands manually.

Also "stack", new subcommand was added to "debugvm".

README.rst

@@ -6,7 +6,7 @@ script. However, in some point of time I've decided to rewrite it almost from
 scratch.
 
 Current version of script was written and tested against VBoxManage in version
-5.0.40, and supports all commands (in some extent ;)).
+5.1.26, and supports all commands (in some extent ;)).
 
 Unlike other attempts, I've tried to make the script context aware. See the
 simple session with the VBoxManage command below, to have an idea how it works:

VBoxManage

@@ -4,6 +4,7 @@
 # URL: https://bitbucket.org/gryf/vboxmanage-bash-completion
 # URL: https://github.com/gryf/vboxmanage-bash-completion
 # License: 3-clause BSD-style license (see LICENSE file)
+# Version: 5.1.26
 
 _VBoxManage() {
     local cur prev opts cmd subcommand tmp items name index result
@@ -440,6 +441,10 @@ _VBoxManage() {
         sort | \
         uniq)
 
+    # add debugvm command manually, since it's described differently in
+    # vboxmanage help
+    opts="${opts} debugvm"
+
     if [[ ${cur} == "-q" || ${COMP_CWORD} -eq 1 ]] ; then
         COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
         return 0
@@ -805,9 +810,9 @@ _VBoxManage() {
             fi
             ;;
 
-        debugvm)
+        "debugvm")
             items=(dumpguestcore info injectnmi log logdest logflags osdetect
-            osinfo osdmesg getregisters setregisters show statistics)
+            osinfo osdmesg getregisters setregisters show statistics stack)
             if [[ ${prev} == ${cmd} ]]; then
                 _vms_comp runningvms
             else
@@ -824,7 +829,7 @@ _VBoxManage() {
                             _get_excluded_items "${items[@]}"
                             COMPREPLY=( $(compgen -W "$result" -- ${cur}) )
                             ;;
-                        getregisters|setregisters)
+                        getregisters|setregisters|stack)
                             _get_excluded_items "--cpu"
                             COMPREPLY=( $(compgen -W "$result" -- ${cur}) )
                             ;;
@@ -835,7 +840,7 @@ _VBoxManage() {
                             COMPREPLY=( $(compgen -W "$result" -- ${cur}) )
                             ;;
                         statistics)
-                            items=(--reset --pattern)
+                            items=(--reset --pattern --descriptions)
                             _get_excluded_items "${items[@]}"
                             COMPREPLY=( $(compgen -W "$result" -- ${cur}) )
                             ;;
@@ -848,7 +853,6 @@ _VBoxManage() {
                             COMPREPLY=( $(compgen -W "$result" -- ${cur}) )
                             ;;
                     esac
-                    _get_excluded_items "--descriptions"
                     COMPREPLY+=( $(compgen -W "$result" -- ${cur}) )
                 else
                     [[ "${prev}" == "--filename" ]] && \