From James Harvey (via a period of collaborative polishing), a patch

to add two kinds of Penrose tiling to the grid types supported by
Loopy.

This has involved a certain amount of infrastructure work, because of
course the whole point of Penrose tilings is that they don't have to
be the same every time: so now grid.c has grown the capacity to
describe its grids as strings, and reconstitute them from those string
descriptions. Hence a Penrose Loopy game description consists of a
string identifying a particular piece of Penrose tiling, followed by
the normal Loopy clue encoding.

All the existing grid types decline to provide a grid description
string, so their Loopy game descriptions have not changed encoding.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@9159 cda61777-01e9-0310-a592-d414129be87e