Merge pull request #219 from serialvelocity94/master

Removed stray argument.
Replaced Free Getopt with getopt_port.
Removed superfluous display sorting.
Made NSScreen to CGDisplay matching fail softly.
Added comment on headless Macs.
Renamed monitor helper functions for clarity.
Initial drag and drop support.
Cleanup.
Fixed broken calls to memset.
Fixed broken includes.
Fixed off-by-one error.
Added drop reporting to events test.
Cleaned up drop callback design.
Added XDND note to conformance page.
Updated title of X11 conformance section.
Added mention of encoding to GLFWdropfun.
X11 conformance updates.
Added extensions to X11 conformance section.
Added file drop support to news page.
Moved internal context function declarations.