Ruby uses a recursive algorithm for handling control/meta escapes
in strings (read_escape). However, the equivalent code for regexps
(tokadd_escape) in did not use a recursive algorithm. Due to this,
Handling of control/meta escapes in regexp did not have the same
behavior as in strings, leading to behavior such as the following
returning nil:
```ruby
/\c\xFF/ =~ "\c\xFF"
```
Switch the code for handling \c, \C and \M in literal regexps to
use the same code as for strings (read_escape), to keep behavior
consistent between the two.
Fixes [Bug #14367]
* Other ruby implementations use the spec/ruby directory.
[Misc #13792] [ruby-core:82287]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59979 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
