x11: Add some missing API

The functions:
XClearWindow
XCreatePixmap
XSetWindowBackgroundPixmap

The XSetCloseDownMode enumerations

The following events:
FocusChangeEvent
ExposeEvent
GraphicsExposeEvent
NoExposeEvent
VisibilityEvent
ResizeRequestEvent
SelectionClearEvent
SelectionRequestEvent
ColormapEvent
MappingEvent
ErrorEvent
KeymapEvent

Fixes bug 727113