gschem: Make sure to distribute x_swatchcr.h.

Fixes breakage introduced in eb910fde814d.
libgeda: [WIP] Add an EdaRtree data structure.

An R*-tree implementation.  This will replace the existing tile
mechanism.

Beckmann, N.; Kriegel, H. P.; Schneider, R.; Seeger, B. (1990). "The
R*-tree: an efficient and robust access method for points and
rectangles". http://dx.doi.org/10.1145/93597.98741

Guttman, A. (1984). "R-Trees: A Dynamic Index Structure for Spatial
Searching". http://dx.doi.org/10.1145/602259.602266