I am trying to install some plugins , and some programs and it is happing almost the same thing: This occur when i try to install Sim :

checking size of char... 1
checking for dlopen in -ldl... yes
checking for shl_unload in -ldld... no
not using lib directory suffix
checking for X... configure: error: Can't find X includes. Please check your installation and add the correct paths!

I check for the XFree86 and i have this packages:
XFree86-Mesa-libGL-4.3.0-2
XFree86-xfs-4.3.0-2
XFree86-100dpi-fonts-4.3.0-2
XFree86-4.3.0-2
XFree86-xdm-4.3.0-2
XFree86-libs-data-4.3.0-2
XFree86-font-utils-4.3.0-2
XFree86-truetype-fonts-4.3.0-2
XFree86-75dpi-fonts-4.3.0-2
XFree86-Mesa-libGLU-4.3.0-2
XFree86-twm-4.3.0-2
XFree86-libs-4.3.0-2
XFree86-base-fonts-4.3.0-2
XFree86-xauth-4.3.0-2
XFree86-tools-4.3.0-2


What is wrong??? What do i do???

Thanks Dan