if an absolute path is given for an internal client load name, use it by just appending ".so"

we used to still look in ADDON_DIR, which might be "secure" but is a bit pointless and inconvenient
fix up internal MIDI client to do duplex
use -I rather than -L to load internal clients from the command line, to be consistent with jack2
move alsa midi internal client into subdir of tools
moved alsa midi internal client into tools
update submodules