Major patch from Thomas Lockhart <Thomas.G.Lockhart@jpl.nasa.gov>

OK, here are a passel of patches for the geometric data types.
These add a "circle" data type, new operators and functions
for the existing data types, and change the default formats
for some of the existing types to make them consistant with
each other. Current formatting conventions (e.g. compatible
with v6.0 to allow dump/reload) are supported, but the new
conventions should be an improvement and we can eventually
drop the old conventions entirely.

For example, there are two kinds of paths (connected line segments),
open and closed, and the old format was

'(1,2,1,2,3,4)' for a closed path with two points (1,2) and (3,4)
'(0,2,1,2,3,4)' for an open path with two points (1,2) and (3,4)

Pretty arcane, huh? The new format for paths is

'((1,2),(3,4))' for a closed path with two points (1,2) and (3,4)
'[(1,2),(3,4)]' for an open path with two points (1,2) and (3,4)

For polygons, the old convention is

'(0,4,2,0,4,3)' for a triangle with points at (0,0),(4,4), and (2,3)

and the new convention is

'((0,0),(4,4),(2,3))' for a triangle with points at (0,0),(4,4), and (2,3)

Other data types which are also represented as lists of points
(e.g. boxes, line segments, and polygons) have similar representations
(they surround each point with parens).

For v6.1, any format which can be interpreted as the old style format
is decoded as such; we can remove that backwards compatibility but ugly
convention for v7.0. This will allow dump/reloads from v6.0.

These include some updates to the regression test files to change the test
for creating a data type from "circle" to "widget" to keep the test from
trashing the new builtin circle type.