-dnl Prepare to support X. If the user gave the command-line option
-dnl --without-x, AC_PATH_XTRA will set no_x to "yes". Otherwise, it will
-dnl add appropriate preprocessor flags to X_CFLAGS, and appropriate linker
-dnl flags to X_LIBS. It also checks for system-specific X libraries, and
-dnl adds them to X_PRE_LIBS or X_EXTRA_LIBS, as appropriate. (The former
-dnl is where "-lSM -lICE" goes, in X11R6.) We define the X_TOOLKIT_LIBS
-dnl and X_BASIC_LIBS argument vectors ourselves, and if X is to be
-dnl supported, we'll concatenate the whole lot of these into a command line
-dnl for libtool. See, e.g., the libplot_la_LIBADD line in
-dnl libplot/Makefile.am.
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