frontend: recognize key_length as an OFFieldLengthMember
diff --git a/loxi_front_end/frontend.py b/loxi_front_end/frontend.py
index 545b5bc..bc79ed9 100644
--- a/loxi_front_end/frontend.py
+++ b/loxi_front_end/frontend.py
@@ -52,10 +52,11 @@
         if m_ast[2] == 'length' or m_ast[2] == 'len': # Should be moved to parser
             return ir.OFLengthMember(name=m_ast[2], oftype=get_type(m_ast[1], ctx))
         elif m_ast[2] == 'actions_len':
-            # HACK only usage so far
             return ir.OFFieldLengthMember(name=m_ast[2], oftype=get_type(m_ast[1], ctx), field_name='actions')
         if m_ast[2] == 'version': # Should be moved to parser
             return ir.OFVersionMember(name=m_ast[2], oftype=get_type(m_ast[1], ctx))
+        elif m_ast[2] == 'key_length':
+            return ir.OFFieldLengthMember(name=m_ast[2], oftype=get_type(m_ast[1], ctx), field_name='key')
         else:
             return ir.OFDataMember(name=m_ast[2], oftype=get_type(m_ast[1], ctx))
     elif m_ast[0] == 'discriminator':