tests/extmod: Improve re1.5/recursiveloop.c test coverage.

tests/extmod/ure1.py

@@ -72,6 +72,11 @@ m = re.match('^ab$', 'ab'); print(m.group(0))
 m = re.match('a|b', 'b');   print(m.group(0))
 m = re.match('a|b|c', 'c'); print(m.group(0))
 
+# Case where anchors fail to match
+r = re.compile("^b|b$")
+m = r.search("abc")
+print(m)
+
 try:
     re.compile("*")
 except: