Switch completely to the table based lexer

Rakefile

@@ -41,10 +41,17 @@ end
 
 desc 'Convert previous stage language into the current stage language'
 task :convert do
-  File.open('boot/stage10.elna', 'w') do |current_stage|
-    File.readlines('boot/stage9.elna').each do |line|
-      current_stage << line
+  File.open('boot/stage14.elna', 'w') do |current_stage|
+    previous_line = nil
+
+    File.readlines('boot/stage13.elna').each do |line|
+      if !previous_line.nil? && previous_line.start_with?('begin') && line.strip.start_with?('return')
+      else
+        current_stage << previous_line unless previous_line.nil?
       end
+      previous_line = line
+    end
+    current_stage << previous_line
   end
 end