presence_dialoginfo: Makefile - try to use pkg-config if xml2-config is not found

src/modules/presence_dialoginfo/Makefile

@@ -1,4 +1,4 @@
-# 
+#
 # WARNING: do not run this directly, it should be run by the master Makefile
 
 include ../../Makefile.defs
@@ -7,6 +7,12 @@ NAME=presence_dialoginfo.so
 
 ifeq ($(CROSS_COMPILE),)
 XML2CFG=$(shell which xml2-config)
+ifeq ($(XML2CFG),)
+XML2CFG=$(shell \
+	if pkg-config --exists libxml-2.0; then \
+		echo 'pkg-config libxml-2.0'; \
+	fi)
+endif
 endif
 
 ifneq ($(XML2CFG),)