Which X11 is missing?

[leonp at plris.com]

Hello. After the HD crash I try to reinstall everything in new Fedora 20
installation.
I installed all libraries as required in the
http://techbase.kde.org/KDevelop4/HowToCompile.
I also tested that libX11 and libX11-devel are installed.
But compilation of kdevelop (kdevplatform compiled OK) finishes with:
[root at leonp build]# cmake ../
-- Found Qt-Version 4.8.5 (using /usr/bin/qmake-qt4)
CMake Error at /usr/share/kde4/apps/cmake/modules/FindX11.cmake:390
(MESSAGE):
  Could not find X11
Call Stack (most recent call first):
  /usr/share/kde4/apps/cmake/modules/Qt4ConfigDependentSettings.cmake:30
(FIND_PACKAGE)
  /usr/share/kde4/apps/cmake/modules/FindQt4.cmake:1207 (INCLUDE)
  /usr/share/kde4/apps/cmake/modules/FindKDE4Internal.cmake:420
(find_package)
  /usr/share/cmake/Modules/FindKDE4.cmake:95 (find_package)
  CMakeLists.txt:17 (find_package)

Please, help. Thanks.