libx11-dev 6.8.2-10.3 (amd64 binary) in ubuntu hoary

 Header files and a static version of the X11 library ("Xlib") are provided by
 this package.
 .
 See the libx11-6 package for further information.
 .
 Ideally, this package would not depend on any extension headers, as Xlib is
 designed to implement only the core X protocol. Nevertheless, some parts of
 Xlib have acquired references to extension headers over the years.
 Specifically, header files for the BIG-REQUESTS, XKEYBOARD, XInputExtension,
 and XC-MISC extensions are used internally. These dependencies are not
 exposed via Xlib's own external interfaces.