configure.ac: use MPD_DEPENDS for upnp->expat dependency

configure.ac

@@ -796,18 +796,14 @@ AM_CONDITIONAL(ENABLE_BZIP2_TEST, test x$BZIP2 != xno)
 
 dnl ---------------------------------- libupnp ---------------------------------
 
-if test x$enable_expat = xno; then
-	if test x$enable_upnp = xauto; then
-		AC_MSG_WARN([expat disabled -- disabling UPnP])
-		enable_upnp=no
-	elif test x$enable_upnp = xyes; then
-		AC_MSG_ERROR([expat disabled -- required for UPnP])
-	fi
-fi
-
 MPD_ENABLE_AUTO_PKG_DEPENDS(upnp, UPNP, [libupnp],
 	[UPnP client support], [libupnp not found], [],
-	[enable_database], [Database support is disabled])
+	[enable_database], [Database support is disabled], [
+		MPD_DEPENDS([enable_upnp], [enable_expat],
+			[UPnP client support],
+			[UPnP requires expat])
+	]
+)
 
 dnl --------------------------------- libzzip ---------------------------------
 MPD_ENABLE_AUTO_PKG(zzip, ZZIP, [zziplib >= 0.13],

m4/mpd_auto.m4

@@ -178,8 +178,10 @@ AC_DEFUN([MPD_ENABLE_AUTO_HEADER], [
 
 dnl Wrapper for MPD_ENABLE_AUTO_PKG and MPD_DEPENDS
 dnl
-dnl Parameters: varname1, varname2, pkg, description, errmsg, default, dep_variable, dep_errmsg
+dnl Parameters: varname1, varname2, pkg, description, errmsg, default, dep_variable, dep_errmsg, pre
 AC_DEFUN([MPD_ENABLE_AUTO_PKG_DEPENDS], [
-	MPD_ENABLE_AUTO_PKG([$1], [$2], [$3], [$4], [$5], [$6],
-		[MPD_DEPENDS([enable_$1], [$7], [$4], [$8])])
+	MPD_ENABLE_AUTO_PKG([$1], [$2], [$3], [$4], [$5], [$6], [
+		$9
+		MPD_DEPENDS([enable_$1], [$7], [$4], [$8])
+	])
 ])