Added mpd plugin

check for missing mpdscribble
one-time warning to plugin
alias m=mpc, + checks for mpc
fixed alias for mpd
formatted accordingly with Style guide.

plugins/mpd/mpd.plugin.zsh

@@ -0,0 +1,35 @@
+let _mpdscribble_missing_warned
+let _mpc_missing_warned
+alias m=mpc
+for _ in 1; do
+  pidof mpdscribble > /dev/null
+  test "$?" = 0 && break
+  _pth=$(which mpdscribble) > /dev/null
+  _exists_mpdscribble=$?
+  test ${_exists_mpdscribble} -eq 0 && let _mpdscribble_missing_warned=0
+  test ${_exists_mpdscribble} -ne 0 \
+	  && test 1 -le "${_mpdscribble_missing_warned}" \
+	  &&  break
+  if [ ${_exists_mpdscribble} -ne 0 ]; then
+    echo "mpdscribble missing"
+    let _mpdscribble_missing_warned+=1
+    export _mpdscribble_missing_warned
+    break
+  fi
+  _exists_mpc=$?
+  test ${_exists_mpc} -eq 0 && let _mpc_missing_warned=0
+  test ${_exists_mpc} -ne 0 && test 1 -le "${_mpc_missing_warned}" &&  break
+  if [ ${_exists_mpc} -ne 0 ]; then
+    echo "mpc missing"
+    let _mpc_missing_warned+=1
+    export _mpc_missing_warned
+    unalias m
+    break
+  fi
+  test -z "${_p}" && $_pth
+  unset _pmpd
+  unset _exists_mpdscribble
+  unset _pth
+  unset _mpdscribble_missing_warned
+  unset _mpc_missing_warned
+done