Added explanation for #error.
Fixed #if-guard logic and signature for hasPreciseScrollingDeltas.
Merge pull request #102 from shurcooL/patch-1

Fixed OS X precise scrolling delta logic.
Fixed glfwCreateWindow return value semantics.
Added pointer swap macro for callback setters.
Replaced selector test with NSAppKitVersionNumber.
Simplified source file comment headers.
Updated change log.
Fixed window position being incorrect on some WMs.
Added clearing of callbacks on terminate.
Fixed original video mode being overwritten.
Removed cursor centering XFlush hack.
Formatting.
Expanded section on X11 and Mesa packages.
Build documentation improvements.
Build documentation improvements.
Build documentation improvements.
Added NvOptimusEnablement.
Fixed keypad 5 release events.
Allowed characters regardless of modifier keys.