[ruby/rdoc] aligns may include :center

(ruby/rdoc#1247)

ruby/rdoc@cbbf04d6f8

Author: soutaro

lib/rdoc/markup/to_rdoc.rb

@@ -254,7 +254,7 @@ def accept_table header, body, aligns
     end
     aligns = aligns.map do |a|
       case a
-      when nil
+      when nil, :center
         :center
       when :left
         :ljust