Really Slick Screensavers GLX Port

When the configure script is run with --disable-sound, it fails with:

checking for Wand... configure: error: The pkg-config script could not
be found or is too old. Make sure it is in your PATH or set the
PKG_CONFIG environment variable to the full path to pkg-config.

This is because the first use of the PKG_CHECK_MODULES macro in
configure.in is in the
if test "x$enable_sound" != "xno"
section, so is skipped if --disable-sound is given, causing the
pkg-config variables to not be initialized.

The pkg-config documentation warns about this and offers a fix:

Note that if there is a possibility the first call to
PKG_CHECK_MODULES might not happen, you should be sure to
include an explicit call to PKG_PROG_PKG_CONFIG in your
configure.ac

PKG_PROG_PKG_CONFIG([minversion])

The patch we use in the OpenSolaris packages to fix this (just
adding that call unconditionally with the other AC_PROG checks)
is attached.