lilypond-book: Various fixes and improvements

• book_latex.py: Remove unused code

  This was missed in commit 3863f416 (from December 2008).

• book_snippets.py: Improve comment

• lilypond-book: Correctly handle deprecated format of line-width option

  Fixes #3459 (closed).

• lilypond-book: Fix combination of verbatim and quote for LaTeX mode

  If both verbatim and quote options are used for a LilyPond environment, the created LaTeX code starts with

  \begin{quote}
  \noindent
  \begin{verbatim}

  LaTeX's quote environment contains special code to signal the next nested environment that it already has inserted some vertical space. However, \noindent hides this marker. As a consequence, the verbatim environment inserts vertical space again, causing a far too large vertical gap.

  This commit fixes this by not inserting \noindent before \begin{verbatim}. It has a minor side effect, though: If option verbatim is used (without option quote) the vertical space to the previous paragraph slightly increases. Reason is that for code like

  foo
  \begin{verbatim}

  LaTeX's verbatim environment inserts \topsep as the vertical amount of space, while

  foo
  
  \begin{verbatim}

  causes \partopsep to be inserted, which is a slightly larger vertical space.

• lilypond-book: Improve comments and help strings for --left-padding

• lilypond-book: Add LaTeX support for vertically shifting inline images

  This commit adds a new command line option --inline-vshift=VSHIFT and an argument to snippet option inline.

• tex-snippet-options.lytex: Extend tests