bindings: search for "libglfw3", too

OS X Homebrew installs GLFW using this name.
bindings: mask float traps around some C functions on sbcl/darwin

A detailed explanation can be found in glfw-bindings.lisp.
This commit also adds a dependency on alexandria. Since CFFI
already uses alexandria, transient dependencies are unchanged.
bindings: fix C-ARRAY->LIST
example: set *GL-GET-PROC-ADDRESS*
example: add example for key and mouse events
bindings: fix key code values

Some names have changed for consistency with the
names used by GLFW:

key-pad-*  -> kp-*
world*     -> world-*

:LAST was removed because it will never
be generated by GLFW.
Merge pull request #4 from fjl/os-x-fixes

Fixes for OS X