Ship libccd's notice, and keep the rectangle helpers on purpose

libccd is compiled into libakgl.so and is BSD-3-Clause, so the notice has to
travel with the binary form. cmake --install now puts BSD-LICENSE at
share/doc/akgl/BSD-LICENSE.libccd, and the README says which dependency is in
that position and which are not -- everything else in deps/ is either a separate
shared object carrying its own notice, a header, or compiled into nothing.

The plan's last step was to delete akgl_rectangle_points,
akgl_collide_point_rectangle and akgl_collide_rectangles. That step is not taken,
and TODO.md carries the reasoning rather than leaving it to be rediscovered:
akgl_collide_rectangles has two correct callers in the sidescroller asking a
game-level overlap question that wants a bool, and it was fixed two commits into
this same series -- deleting it now would be a strange thing to do to a caller.
The other two are the weak case and are named as the candidates if a 0.9.0 wants
to trim.

akgl_RectanglePoints' comment still claimed akgl_collide_rectangles works corner
by corner, which stopped being true when the cross case was fixed. Corrected in
place, with the cross case named so the note explains why the shape changed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KzBDV2fqgnUAcqCKqKvc71

CMakeLists.txt

@@ -853,6 +853,11 @@ install(FILES ${CMAKE_CURRENT_BINARY_DIR}/akgl.pc DESTINATION "lib/pkgconfig/")
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/include/akgl/version.h DESTINATION "include/akgl/")
 install(TARGETS akgl DESTINATION "lib/")
 install(FILES "deps/semver/semver.h" DESTINATION "include/")
+# libccd is compiled into libakgl.so, and its BSD-3 licence requires the notice
+# to travel with the binary form. Nothing else in deps/ is linked in statically
+# -- SDL, jansson, libakerror and libakstdlib are all separate shared objects
+# that ship their own -- so this is the only third-party notice we owe.
+install(FILES "deps/libccd/BSD-LICENSE" DESTINATION "share/doc/akgl/" RENAME "BSD-LICENSE.libccd")
 foreach(header IN LISTS AKGL_PUBLIC_HEADERS)
   install(FILES "include/akgl/${header}.h" DESTINATION "include/akgl/")
 endforeach()