schema mount UPDATE simplify parsing data in ext callback

Also include an example.

Author: michalvasko

examples/schema_mount/Makefile

@@ -0,0 +1,7 @@
+all: schema_mount_example
+
+schema_mount_example: schema_mount_example.c
+	gcc -Wall -g -o $@ $^ -lyang
+
+clean:
+	rm -f schema_mount_example

examples/schema_mount/config_data.xml

@@ -0,0 +1,15 @@
+<network-instances xmlns="urn:ietf:params:xml:ns:yang:ietf-network-instance">
+    <network-instance>
+        <name>inst0</name>
+        <vrf-root>
+            <routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
+                <control-plane-protocols>
+                    <control-plane-protocol>
+                        <type>direct</type>
+                        <name>prot0</name>
+                    </control-plane-protocol>
+                </control-plane-protocols>
+            </routing>
+        </vrf-root>
+    </network-instance>
+</network-instances>