utils: add a helper class to lit for captured substitutions
utils: add a helper class to lit for captured substitutions

On Windows, if the substitution contains a back reference, it would
removed due to the replacement of the escape character in lit. Create a
helper class to avoid this which will simply ignore the replacement and
mark the substitution as having capture groups being referenced.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@327082 91177308-0d34-0410-b5e6-96231b3b80d8

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