* scm/define-markup-commands.scm (whiteout): do not force

* scm/define-markup-commands.scm (whiteout): do not force
foreground color of argument markup to black.

* scm/stencil.scm (annotate-y-interval): put arrow dimension at
the left of the arrow, instead of below the arrow name, so that,
when two little arrows are vertically stacked, their dimensions
and name should not overlap. Add a color key parameter.

* scm/paper-system.scm (paper-system-annotate): Annotate
next-space+next-padding instead of next-space. Annotate space
between next-padding and next-space+padding, respectively, and
following system extent and refpoint-Y-extent. Use colors.

* scm/page.scm (annotate-page): translate annotations slightly to
the right.