Make the line of sight square.

This implementation is based on the new_squarelos branch of Stone Soup,
written by elliptic <hyperelliptical@gmail.com>.

The (chronologically-ordered) log entries for the non-merge commits
unique to that branch follow:

commit 9a2a67f80ac0ad70b4bed721160264b9b80f2efc
Author: elliptic <hyperelliptical@gmail.com>
Date:   Sun Oct 23 02:28:06 2011 -0400

    Square LOS.

    It seems functional for basic things, at least. I used rob's old squarelos
    implementation as a model (meaning that LOS radius is 7 and most ranges
    between 4 and 8 were lowered by 1) and basically purged all the circlelos
    effects that I could find that were straightforward to turn into squarelos.

    Current issues include:
    * halos (and other area effects)
    * blood and web sensing effects
    * noise
    * EUCLIDEAN compile-time option (makes no sense now)
    * tornado
    * explosions, including the storms
    * cloud spells
    * and probably many other things!

commit eb3fe9d2367a608d9fa3009f6ed1ca81f7eb8978
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 01:41:17 2011 -0400

    Make halo-type effects square.

    Includes silence, liquefaction, halo, umbra, sanctuary, and orb glow.

commit abe8dfbf850a9717d9d52f3c2823898f548a52d0
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 02:09:02 2011 -0400

    Make clouds expand along diagonals just as easily as along non-diagonals.

    This isn't very noticeable except in open areas, where it makes clouds a
    tiny bit less reliable.

commit 2aad6e7dbc4e77336a3838c629b23468e9ba55be
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 02:33:31 2011 -0400

    Attempt to rebalance the storms a little.

    There are probably better ways of compensating for squares being larger than
    circles, but for the moment let's lower the chance of getting radius 3 for a
    storm. New chance pow/1000, old chance (pow-76)/pow.

commit 5589c58ccb7564f802f8017e1b4b1d6624a4b6cd
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 04:27:33 2011 -0400

    Square tornado.

    No effort to rebalance Tornado yet - it is likely a good idea to make it max
    out at radius 5.

commit 28209710c756efb54693af2364ab94248964c874
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 04:50:11 2011 -0400

    Replace PI with 3 for Tornado rotation purposes.

commit 036fca2aba64d888686a1377fc72ab122b86c776
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 05:12:27 2011 -0400

    Make a few distance_iterators squarer.

commit d015de04215de13ce6a8898075e8cbeba55f9a48
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 13:42:55 2011 -0400

    Make some abyss effects squarer.

    The actual Worley noise abyss generation should be unchanged.

commit b35f82ae63fbad98e6aca1a2a50b9f23bf5d48ce
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 13:49:06 2011 -0400

    Change the default metric for distance_iterator.

    Since now it is using the same one everywhere...

commit 385c37b77bb5afbb1ad7f040e053ea2c90153955
Author: elliptic <hyperelliptical@gmail.com>
Date:   Mon Oct 24 14:04:19 2011 -0400

    Make web-sensing and blood-smelling squarer.

commit a202c03c705d0903906a03b5a318faaeae0f01d4
Author: elliptic <hyperelliptical@gmail.com>
Date:   Fri Oct 28 18:27:55 2011 -0400

    Make noise squarer.

    This might make noise noticeably louder, but there have been complaints for
    a few versions now about it being too weak.