Optimize get_path_list. (issue 579570043 by address@hidden)

[dak]

There is scm_c_memq for avoiding hare&tortoise, but for this use case,
the explicit code seems like the saner option.  Even without
hare&tortoise, the list would be consed together each time without
further measures.


https://codereview.appspot.com/579570043/diff/577750045/lily/stencil-integral.cc
File lily/stencil-integral.cc (right):

https://codereview.appspot.com/579570043/diff/577750045/lily/stencil-integral.cc#newcode115
lily/stencil-integral.cc:115: && (SCM_EQ_P (head, ly_symbol2scm
("moveto"))
SCM_EQ_P is an old deprecated macro.  Use scm_is_eq instead.  Same
performance.

https://codereview.appspot.com/579570043/diff/577750045/lily/stencil-integral.cc#newcode127
lily/stencil-integral.cc:127: return get_path_list (scm_cdr (l));
Not caused by this patch, but this does look like something nicer
addressed by a loop rather than tail recursion with regard to C++
idioms.

https://codereview.appspot.com/579570043/