* scm/ps-to-png.scm (make-ps-images): cleanup multipage vs. single

* scm/ps-to-png.scm (make-ps-images): cleanup multipage vs. single
page switch.

* make/lilypond-vars.make (LILYPOND_BOOK_FLAGS): set
anti-alias-factor for lilypond-book runs.

* scm/ps-to-png.scm (scale-down-image): new function.
(my-system): new function.
(make-ps-images): blow up GS resolution by anti-alias-factor,
scale down image by anti-alias-factor.  This improves appearance
of
(make-ps-images): remove showpage. Fixes spurious empty png at end.

* scm/lily.scm (lambda): default resolution 116 (8 pixels per
space).