Update Clang requirement

I built a Clang 3.1 to test with; it gave a fixable error, followed
by crashing on lots of code, which sounds familiar from last time I
tried that version of Clang on Lasercake (it worked at some code
states...).  Probably not worth supporting it.  Yell if you're stuck
on a version of Xcode with a Clang snapshot that can't quite build this
and if you can't use compilers from Macports?  Let me know if this is
a common situation.
Merge branch 'master' of https://github.com/elidupree/Lasercake
make BOOST_CHECK test failures look better
restore std::boolalpha by default.
fix incomplete header includes (revealed by trying to make tests)
start to add patricia trie tests, and fix one
AGPL, as agreed by us; and update copyright notices.
fix world selection
Make Ctrl/Cmd-W also close the window.
add patricia_trie_tests
extra check on int sizes
patricia_trie refactoring/testing work
Merge branch 'master' of https://github.com/idupree/Lasercake
Tweaked HUD text
fixed left/right rotation changing up/down angle