counsel.el (counsel-unquote-regex-parens): Improve

counsel.el (counsel-unquote-regex-parens): Improve

* counsel.el (counsel-grep-function): Use different quoting. Now it's
  possible to use e.g. "(defun foo" as input.
(counsel-unquote-regex-parens): Does the proper unquote now - 4
replacements instead of previous 2.

* ivy-test.el (counsel-unquote-regex-parens): Add test.