[git-imerge] Bump to experimental branch

From mrhacky's experimental branch (plus a chmod +x fix, so it's on
neph's upstream)
[bin/ffbrun] Fix -x after --profile addition
[bin/nightfox] | nightfox -grp | should work
[git] Add git cm alias (commit -m)
[moz/cfg] Enable ipdl tests in debug by default
[bin/ls++] Fix, add wrapper, works now
[README] Add note for ls++.conf
[emacs] Add markdown-mode