yanglint FEATURE initial version of yanglint(1)

Source codes are mostly taken from libyang 1.0 and slightly modified for
libyang 2.0. A lot of functionality is still missing since it is not yet
provided by libyang 2.0
diff --git a/tools/lint/examples/module2.yin b/tools/lint/examples/module2.yin
new file mode 100644
index 0000000..af6cb50
--- /dev/null
+++ b/tools/lint/examples/module2.yin
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module name="module2"
+        xmlns="urn:ietf:params:xml:ns:yang:yin:1"
+        xmlns:m="urn:yanglint:module">
+  <namespace uri="urn:yanglint:module"/>
+  <prefix value="m"/>
+  <leaf name="m">
+    <type value="string"/>
+  </leaf>
+</module>