Implement non-standard tuplet numbers

Implement non-standard tuplet numbers
-) Add function for different fraction than the actual tuplet fraction
-) Add wrapper function that appends a note with given duration after
   the standard tuplet text (denominator or fraction)
-) Add function to print tuplet text with both fraction values with a
   note duration attached
-) Add snippet to be included in the Docs
-) Add regtests for all these cases
-) Remove definitions from musicxml2ly and make it use these new functions

[hanwenn, 2009-02-20 14:45:04]

lgtm

http://codereview.appspot.com/12661/diff/1/11
File scm/output-lib.scm (right):

http://codereview.appspot.com/12661/diff/1/11#newcode307
Line 307: (define-public ((tuplet-number::append-note-wrapper function note)
grob)
rename function to describe what it does.

http://codereview.appspot.com/12661/diff/1/11#newcode322
Line 322: (define-public ((tuplet-number::non-default-tuplet-fraction-text
denominator numerator) grob)
maybe you can make these optional? 

  (func arg arg1 . opt-args)

there are also std libs to make functions with keyword arguments.  Maybe you can
use those to fold some of the functions together.

[Reinhold, 2009-02-20 19:42:27]

http://codereview.appspot.com/12661/diff/1/11
File scm/output-lib.scm (right):

http://codereview.appspot.com/12661/diff/1/11#newcode307
Line 307: (define-public ((tuplet-number::append-note-wrapper function note)
grob)
On 2009/02/20 14:45:04, hanwenn wrote:
> rename function to describe what it does.

This is a wrapper function, which simply appends a note to the output of the
wrapped function, so this name was the best I could come up to describe what it
does.

http://codereview.appspot.com/12661/diff/1/11#newcode322
Line 322: (define-public ((tuplet-number::non-default-tuplet-fraction-text
denominator numerator) grob)
I'm not sure if we can merge some functions. We need a function for numerator
only, one function for fraction, and two functions that print the note with the
numbers. The only two cases that can be merged is
tuplet-number::calc-denominator-text and
(tuplet-number::non-default-tuplet-denominator-text denominator), and similarly
for fractions. However, this requires a syntax change, since then one could no
longer set the property to tuplet-number::calc-denominator-text for the default
tuplet number, but has to use (tuplet-number::calc-denominator-text) instead. I
prefer not to do this.
Of course, I can still make the numerator and maybe also the denominator
optional in this case, but we can't really get rid of a function.