Don't include method documentation for aliased methods

[peterzhu2118]

In Ruby, the documentation guide states:

Omit aliases from the call-seq, unless the alias is an operator method.

This is intended prevent documentation duplication and have the reader read the documentation for the original method. However, this leads to all of the aliases to not have call-seq so the method appears to accept no arguments and is misleading to the reader (e.g. Array#find and the alias Array#detect appears to take no arguments).

I think RDoc should (at least have the option to) avoid generating documentation for aliased methods.

(This discussion originated from ruby/ruby#15756)