add ly:book-set-header!

add ly:book-set-header!

Add a scheme function ly:book-set-header! like ly:score-set-header!

Function is copied from score-scheme.cc to book-scheme.cc,
setting public member var header_ in class Book.

[janek, 2012-03-03 00:42:25]

From Jan-Peter Voigt, please review:

Hello list,

sorry for resending this, it might get lost, because I simply answered to
another thread with another subject.

now, we have a book-predicate and we are dealing with books in scheme. Then we
might want to set a header after creating a book.
There is a function ly:score-set-header!, which I copied and adapted for the
Book-class.
This patch compiled and works with the following snippet.

--snip--
\version "2.15.32"

bk = \book {
 \score {
   \relative c' {
     c4 e g b
   }
 }
}

#(let ((bh (eval-string "(define-module (a b))")))
    (eval '(define title "Hallo") bh)
    (ly:book-set-header! bk bh))

\book { \bk }
--snip--

Is this helpful for lily-devel?
And is there another (better) way of creating a module (for header generation)
on the fly in scheme?

[janek, 2012-03-30 09:38:21]

This was pushed as 744709d5ce7c67890c5c79f359f885a09cc26f27.