Web-fr: updates community, intro and manuals
Doc-fr: updating extending and usage

 - scheme-tutorial
 - running
Doc-fr: updating LM

 - common-notation
 - templates
Doc-fr: updating NR

 - notation
 - ancient
 - appendices
 - vocal
Merge remote-tracking branch 'origin/master' into translation
Doc-es: some nits.
Doc-fr: updates LM, NR and extending
Issue 3093: Declare absolute-volume-alist and instrument-equalizer-alist as session-local

At least instrument-equalizer-alist is advertised as sort of a
user-settable variable, and while we ask users to tamper with it, we
might as well restore it at the beginning of next session.  This does
not really replace a proper user interface instead of the pathetic
excuse we have for it now.
Doc: update translation status.
Doc-es: udpate CHANGES, Programming, Scheme tutorial, Notation appendices.
Doc-es: update Common Notation.
Doc-es: update Fundamental, Editorial, Expressive, Fretted.
Doc-es: update Keyboards, Percussion, Staff, Text.
Doc-es: update Vocal.
Issue 3102: Allow EOF to occur in the middle of a line comment
Doc: clarify example of 'Going back in MIDI time' (3097)

  Add a note before the acciaccatura, because, in order to
  understand the error (and the solution), you need to compare
  the whole duration of the acciaccatura block with the duration
  of the previous note.  (Thanks Federico!)
Web-es: update, except NEWS.
factor out some duration processing

New functions duration-log-factor, duration-dot-factor, duration-length,
duration-visual, and duration-visual-length.  All concerned with low-level
numerical processing of durations, so that other code doesn't have to
understand dot counts and the like.
Web-es: update NEWS.
Doc-es: update Learning/Tweaks.