Update yarv compiler and decompiler to stop using Elsif node

Author: egiurleo

lib/syntax_tree/yarv/compiler.rb

@@ -911,17 +911,6 @@ def visit_else(node)
         iseq.pop unless last_statement?
       end
 
-      def visit_elsif(node)
-        visit_if(
-          IfNode.new(
-            predicate: node.predicate,
-            statements: node.statements,
-            consequent: node.consequent,
-            location: node.location
-          )
-        )
-      end
-
       def visit_ensure(node)
       end
 
@@ -1057,7 +1046,8 @@ def visit_if_op(node)
                 statements: node.falsy,
                 location: Location.default
               ),
-            location: Location.default
+            location: Location.default,
+            beginning: "if"
           )
         )
       end

lib/syntax_tree/yarv/decompiler.rb

@@ -77,7 +77,7 @@ def decompile(iseq)
               Next(Args([]))
             ]
 
-            clause << IfNode(clause.pop, Statements(body), nil)
+            clause << IfNode(clause.pop, Statements(body), nil, "if")
           when Dup
             clause << clause.last
           when DupHash