x-window-system-dev 6.8.2-77.2 (amd64 binary) in ubuntu breezy

 This metapackage provides the components of the X Window System as developed
 by the X.Org Project which are most interesting to programmers.
 .
 X Window System design documentation, manual pages, library reference works,
 unstripped and static versions of the shared libraries, C header files, and
 special versions of libraries available only in static form (with and without
 PIC symbols included) are supplied by the packages depended on by this
 metapackage.
 .
 This also provides header files for almost all extension protocols.