Implement framework for post-fix text (de)cresc spanners (backend only)

[n . puttock]

LGTM.

Don't forget to add 'span-text to all-music-properties.


http://codereview.appspot.com/109072/diff/1/2
File input/regression/dynamics-custom-text-spanner-postfix.ly (right):

http://codereview.appspot.com/109072/diff/1/2#newcode1
Line 1: \version "2.13.1"
2.13.4

http://codereview.appspot.com/109072/diff/1/2#newcode4
Line 4: texidoc = "Postfix functions for custom crescendo text spanners.
The spanners should
two spaces after full stop

http://codereview.appspot.com/109072/diff/1/2#newcode13
Line 13: )
lonely parenthesis

(same below)

http://codereview.appspot.com/109072/diff/1/2#newcode18
Line 18: \relative c' { c4-\mycresc "custom cresc" c4 c4 c4 |
newline after {

http://codereview.appspot.com/109072/diff/1/3
File input/regression/dynamics-text-spanner-postfix.ly (right):

http://codereview.appspot.com/109072/diff/1/3#newcode1
Line 1: \version "2.13.1"
2.13.4

http://codereview.appspot.com/109072/diff/1/3#newcode5
Line 5: produce one text spanner. Defining custom spanners is also
easy."
two spaces after full stop

http://codereview.appspot.com/109072/diff/1/3#newcode9
Line 9: crpoco = #(make-music 'CrescendoEvent 'span-direction START
'span-type 'text 'span-text "cresc. poco a poco")
long lines

http://codereview.appspot.com/109072/diff/1/3#newcode14
Line 14: \relative c' { c4\cresc d4 e4 f4 |
newline after {

http://codereview.appspot.com/109072/diff/1/4
File lily/new-dynamic-engraver.cc (right):

http://codereview.appspot.com/109072/diff/1/4#newcode22
Line 22: #include "misc.hh"
You're not using camel_case_to_lisp_identifier (), so this can be
removed

http://codereview.appspot.com/109072/diff/1/4#newcode37
Line 37: SCM get_property_setting (Stream_event *evt, const char
*evprop, const char *ctxprop);
char const *

shorten line

http://codereview.appspot.com/109072/diff/1/4#newcode77
Line 77: //   SCM spanner_type = evt->get_property (name);
remove

http://codereview.appspot.com/109072/diff/1/4#newcode79
Line 79: if (spanner_type == SCM_EOL) {
remove { }

http://codereview.appspot.com/109072/diff/1/4#newcode122
Line 122: (start_type + "Spanner").c_str ());
fix indent

http://codereview.appspot.com/109072/diff/1/4#newcode131
Line 131: (start_type + "Text").c_str ());
fix indent

http://codereview.appspot.com/109072