One-line-auto-height page breaking

The ly:one-line-auto-height-breaking function works just like ly:one-line-breaking except the page height is automatically modified to fit the height of the music. Specifically, the paper-height variable in the \paper block is set so that it spans the height of the tallest score plus the top-margin and bottom-margin.

Note that the top-system-spacing setting will affect the vertical position of the music. Set it to #f in a paper block to simply place the music between the top and bottom margins.