Added namedGroups property to Regex struct.

Extended NamedGroupRange to be a random access and forward range, and added length memeber.

Changed name of namedGroups property to namedCaptures
Add workaround to fix issue 10567

Currently VariantN does not support const objects comparison. So just add specialized opCmp member and use cast().
Improve byLine doc

Move byLine examples from ByLine to byLine.
Fix LinesReader typo.
Explain that lines will not persist when using a mutable type for Char.
Document parameters.
Merge pull request #1405 from 9rnsr/fix10567

Add workaround to fix issue 10567
Make byLine return an opaque type

File.ByLine is still visible for backwards compatibility, but no longer
documented.
Merge pull request #1385 from blackwhale/named-regex

Added namedGroups property to Regex struct.
s/forward range/input range/ plus minor fixes
Merge pull request #1408 from ntrel/byLine-doc

Improve byLine doc