Fix possibly broken toolbar_compose.xml by migrating A_SENDL actions names

to A_SEND_LATER. An attempt to rewrite the whole toolbar .xml file was done
when only a part of it was read, leading to toolbar elements loss; the
rewrite of migrated toolbar configs is now done a posteriori.
Also, the renaming/migration magics swallowed the existing one
for A_SYL_ACTIONS.