Rockbox

Add speech to the browse_id3() screen.

The fact that everything was in a list made it easy: just speak the
current line and let user move to hear the rest. But properly speaking
the various data types took a bit more work.

title, artist, album and genre are spelled.
(Genres are known strings but there's way too many of them to make voice
clips for each. Is there a half-dozen most used that we could do?)

Track number and year are usually a number but are in fact free-form and
given in a string. So I go through the string, saying successive digits
as numbers and spelling anything else. I even made a year unit so it says
"nineteen ninety nine" instead of "one thousand 9 hundred ninety nine".

Length (duration) is said in numbers of hours,minutes,seconds.
Playlist position is spoken as <number> "of" <number>.
Bitrate and frequency are said with appropriate unit.

Replaygain is parsed and if in the expected format, said as a signed
number, dot, fraction numbers spelled, and decibel unit. It the expected
form is not recognized, we just spell everything as a fallback.

Path is said using functionality from my talk_file patch, which I will
upload in a few minutes: it can play the .talk clips for each component
of the path, or just spell the whole thing.

And if no info is available for a particular field, it says so.