vim: remove the ltphon file syntax

The letter-to-phoneme functionality is being revised, so the file
format is no longer designed/used.
vim: add descriptions for the filetypes in the yml
vim: clean up the ftdetect files
cainteoir.man: document the -D/--device option
dictionary.man: document the new/missing options
man: update the date on the .TH line
man: add a manual file for phoneme-converter
Merge branch 'master' into debian