* lib/mkmf.rb (depend_rules): support comments during a line.

* lib/mkmf.rb (depend_rules): apply RULE_SUBST even if the dependency
  file contains path.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48437 b2dd03c8-39d4-4d8f-98ff-823fe69b080e