gschem: Breakout fill properties dialog
build-sys: Add AM_PROG_AR.

AM_PROG_AR is now required by libtool autoconf macros for the creation
of non-POSIX shared objects.
gschem: Ensure variables are always set before use.

Commit 76148e9edaf1 introduced some compiler warnings that variables
may be used uninitialised.  Always initialise them to some sensible
default values.
gschem: Remove some function definitions that are no longer used.

In 283057587a0e, some static functions definitions were deleted from
x_dialog.c, but the corresponding declarations were not cleaned up.
gschem: Correct preprocessor macro collision.

In eb910fde814d, a definition of LINE_WIDTH was added in the new
swatch widget that conflicted (both in meaning and in value) with the
header file definition.
gschem: o_path_draw_rubber() passes uninitialised memory to libgedacairo.

Properly zeroing out the temporary object stops libgedacairo from
printing a big pile of assertion error warnings while dragging path
handles around.
libgeda: Provide a way to create an OBJ_PATH from a PATH structure.

It's sometimes useful to be able to create a path object directly from
a sequence of path sections in a PATH structure rather than by parsing
a string.
gschem: Add ability to interactively draw paths.

Paths have been in gschem for a long time, but there has only been the
ability to edit them (by moving control points) rather than to draw
them by defining a sequence of points.

This patch adds the state machine and rendering infrastructure
required for drawing paths.  Each point in the path is defined by
either clicking in the page (to add a cusp node) or by clicking and
dragging (to add a smooth node).  Paths are finished either by
clicking on the starting point (to close the path) or by clicking on
the last point (to finish an open path).
gschem: Add keybinding and menu entries for "Add Path" function.
gschem: Clean up drawing state on cancelling path creation.
[WIP] To-do list.
[WIP] libgeda: Add OBJ_SPLITTER.
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