Convert a bunch of C++ internals to degrees rather than radians (issue 305380043 by address@hidden)

[thomasmorley65]

As always, can't judge C++ -code.

Though, I've gone through the doc-strings, from that and from
patch-description:
very nice!
Thanks tackling this problem.
I'd love to play around with ly:length, ly:directed and ly:angle.
Regrettable I'll not have enough time to do tests before next weekend.

Found an old typo:




https://codereview.appspot.com/305380043/diff/1/scm/lily-library.scm
File scm/lily-library.scm (right):

https://codereview.appspot.com/305380043/diff/1/scm/lily-library.scm#newcode779
scm/lily-library.scm:779: as rectangular coordinates @ode{(x-length .
y-length)}."
should be: @code

https://codereview.appspot.com/305380043/