fixed xinerama option

configure.in

@@ -423,20 +423,20 @@ AC_ARG_ENABLE(
 dnl Check for Xinerama support
 
 AC_MSG_CHECKING([whether to build support for the Xinerama extension])
-AC_ARG_ENABLE(xinerama,
-[  --enable-xinerama       enable xinerama extension [default=no]], , [enable_xinerama=no])
-
-if test "x$enable_xinerama" = "xyes"; then
+AC_ARG_ENABLE(
+  xinerama,
+[  --enable-xinerama       enable xinerama extension [default=no]], 
+   if test x$enableval = "xyes"; then
 	AC_MSG_RESULT([yes])
 	AC_CHECK_LIB(Xinerama, XineramaQueryScreens,
-			XINERAMA="-DXINERAMA"; Xinerama_libs="-lXinerama", )
-else
+	        AC_DEFINE(XINERAMA, 1, "Xinerama support")
+                LIBS="$LIBS -lXinerama")
+   else
         AC_MSG_RESULT([no])
-fi
-AC_SUBST(XINERAMA)
-CXXFLAGS="$CXXFLAGS $XINERAMA"
+   fi,
 
-LIBS="$LIBS $Xinerama_libs"
+   AC_MSG_RESULT([no])
+)
 
 dnl Determine the return type of signal handlers
 AC_TYPE_SIGNAL