Some packages pay attention to `--enable-feature' options to
configure, where feature indicates an optional part of the
package. They may also pay attention to `--with-package'
options, where package is something like `gnu-as' or `x'
(for the X Window System). The `README' should mention any
`--enable-' and `--with-' options that the package recognizes.
For packages that use the X Window System, configure can usually
find the X include and library files automatically, but if it doesn't,
you can use the configure options `--x-includes=dir'
and `--x-libraries=dir' to specify their locations.