add extra tests for label normalization

Author: tatchi

tests/blackbox/normalize-label.t

@@ -0,0 +1,27 @@
+Case insensitive comparison
+  $ omd << "MD"
+  > [ΑΓΩ]: /url
+  > 
+  > [αγω]
+  <p><a href="/url">αγω</a></p>
+
+Collapse consecutive internal spaces, tabs
+  $ omd << "MD"
+  > [ΑΓ  	Ω]: /url
+  > 
+  > [αγ ω]
+  <p><a href="/url">αγ ω</a></p>
+
+Strip leading and trailing spaces, tabs
+  $ omd << "MD"
+  > [ 	ΑΓΩ  ]: /url
+  > 
+  > [αγω]
+  <p><a href="/url">αγω</a></p>
+
+Doesn't match due to the internal space
+  $ omd << "MD"
+  > [ΑΓΩ]: /url
+  > 
+  > [α γω]
+  <p>[α γω]</p>