Catching unmatched braces

[Trevor Daniels]

Sorry for breaking the doc build again, Neil, and thanks for fixing it.

As I can't build the docs 'properly' under Windows I use texi2html to check 
for errors, but it seems it doesn't flag up unmatched braces like the error 
you just fixed:

For example, if a @notation{rinforzando} dynamic marking,
address@hidden), is required, this will not by default
address@hidden, is required, this will not by default
have any effect on the MIDI volume, as this dynamic marking is not

Reinhold, does the version of texi2html which you are using catch this type 
of error?

Trevor