User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4
Build Identifier: 

If there is no /usr/include/X11 link, some packages won't build, mostly because some files can't find X11/Xlib.h. The packages and the problematic files are:
- libxfcegui4: xfce4-modules/mime-icons/Makefile.am
- xfce-mcs-plugins: plugins/gtk_common/Makefile.am
- xffm: libs/Makefile.am
- xfprint: common/Makefile.am
The solution is:
- libxfcegui4: add @LIBX11_CFLAGS@ to common_FLAGS
- xfce-mcs-plugins: add @LIBX11_CFLAGS@ to libgtkcommon_la_CFLAGS
- xffm: add @LIBX11_CFLAGS@ to common_FLAGS
- xfprint: add @LIBXFCEGUI4_CFLAGS@ to libxfprint_la_CFLAGS

This bug is found in Xfce-4.2.3.2, but today I checked the trunk on the svn web viewer, and it's still there.

Reproducible: Always

Steps to Reproduce:
1. Download sources
2. Remove /usr/include/X11
3. Compile

Actual Results:  
Configure finishes without errors, but make quits because of an error (X11/Xlib.h: No such file...)

Expected Results:  
It should compile correctly.