Improve byChunk, lockingTextWriter doc

Make byChunk, lockingTextWriter return opaque types (but keep those
types public for backward compatibility).
Add byChunk range example.
Also document that ByLine's primitives can throw StdioException.
Improve speed of to!string for integral types
Fix issue 10773.
Add missing signature constraints for splitter.

As well as require bidirectional separator with length before assuming
retro(separator) and separator.length will work.

Without these additional constraints, splitter will cause unhelpful
compile errors about being unable instantiate find, when the separator
is a non-forward input range, or when it doesn't have length, or when
it's non-bidirectional. In the latter case, splitter should still work,
just that it won't export a bidirectional interface.
Fix Issue 5378 - Make File.byLine accept a string terminator

Add an overload of byLine without a default argument for terminator.
Before, byLine!string tried to instantiate "string terminator = '\n'",
which is invalid.

Note: This removes the default arguments from ByLine.this, but the
constructor was never documented anyway (unlike the range primitives).
Add comments for ranges that are no longer documented
Don't need to loop over subranges to use equal().

I wrote it that way 'cos if the subrange is a distinct type from the
original range, equal won't compare them properly (compiler will
complain about == not being defined).

But in this case, it does work, so I rewrote it to use equal() directly.
cleanup std.regex CTFE hacks, it's working as is now
Fix calling ByLine(file) with default args
Ensure terminator string has Char element type
lockingTextWriter should not be a @property
Merge pull request #1456 from quickfur/issue10773

Fix issue 10773.
Use ElementEncodingType!Terminator instead of typeof(terminator[0])
Make std.windows.syserror.sysErrorString @trusted
enable ctRegex tests, fix 3 latent bugs

Bad codegen for Backreferences,
wrong trackers used for nested infinite loops
and even wrong code for '.'
restore "multi-line" behaviour of '.' in ctRegex
catch the wrong test-case
fix faulty multi-line logic of Eol in ctRegex

Also reduce the amount of tests to run to let auto-tester breath freely
Add versioned blocks to partition test-suite in compilable parts
Merge pull request #1464 from blackwhale/ctr-enable-test

Enable ctRegex tests, fix 3 latent bugs
Introduce lookahead for ctRegex