Configure: When configuring examples, make sure we have popt-devel

Add a check for configure that we do have popt-devel available
if --enable-examples is specified.

configure.ac

@@ -33,11 +33,46 @@ AC_ARG_ENABLE([examples],
 	      [ENABLE_EXAMPLES=$enableval],
 	      [ENABLE_EXAMPLES="no"])
 
+# We need popt to compile the examples
 if test x$ENABLE_EXAMPLES = xyes; then
+AC_MSG_CHECKING(whether libpopt is available)
+ac_save_CFLAGS="$CFLAGS"
+ac_save_LIBS="$LIBS"
+CFLAGS="$CFLAGS $GLIB_CFLAGS"
+LIBS="$GLIB_LIBS $LIBS -lpopt"
+AC_TRY_RUN([
+/*
+ * Just see if we can compile/link with popt
+ */
+#include <popt.h>
+
+int main(int argc, const char *argv[])
+{
+	struct poptOption popt_options[] = {
+		POPT_TABLEEND
+	};
+	poptGetContext(argv[0], argc, argv, popt_options, POPT_CONTEXT_KEEP_FIRST);
+
+	return 0;
+}
+], ac_cv_have_popt=yes, ac_cv_have_popt=no,
+   [echo $ac_n "compile with POPT. Assuming OK... $ac_c"
+    ac_cv_have_popt=yes])
+CFLAGS="$ac_save_CFLAGS"
+LIBS="$ac_save_LIBS"
+if test "$ac_cv_have_popt" = yes ; then
+  AC_MSG_RESULT(yes)
   MAYBE_EXAMPLES="examples"
+else
+  AC_MSG_RESULT(no)
+  AC_MSG_NOTICE(You need libpopt to compile the sample libnfs clients.)
+  AC_MSG_NOTICE(Only the library will be compiled and installed.)
 fi
+fi
+
 AC_SUBST(MAYBE_EXAMPLES)
 
+
 AC_ARG_ENABLE(tirpc,
   	[AC_HELP_STRING([--enable-tirpc],
   			[enable use of TI-RPC @<:@default=no@:>@])],