Bugfix in std.conv.parseEscape

parseEscape was not parsing the escapes:
\
0
'
"
?
unittests for parseEscape
Update unittest to take into account...

...Octal escapes and named character entities. These still don't work, but there was a test checking octal would throw, which is wrong.
Fix strideBack for ref ranges.
Added tests for reference type ranges to stride.
Fix for issue# 9456.

This change makes it so that decodeFront takes its range by ref and pops
off the code units that it decodes (unlike decode). It pretty much has
to do that, since it supports input ranges, and they can't do anything
else.
Swap a couple of overloads in std.utf.

This makes no semantic difference to the code, but it makes it so that
the attributes which are on one of the overloads don't make it into the
documentation (where they would imply that all of the overloads have
those attributes, which is not correct).
Minor tweak to decodeFront per review.
Add `std.traits.{isNested,hasNested}`.
Fix `std.traits.FieldTypeTuple` for structs.
Document what exactly `std.traits.FieldTypeTuple` do.
Remove some undocumented, deprecated functions which are slated for removal.

These have been deprecated for a while, but there was some balking
(primarily from Andrei IIRC) at actually removing them when they were
slated for removal, so they were instead made undocumented and slated
for removal after yet another 6 months or so. So, now that that time has
passed, here's another attempt to actually remove them.
fix Issue 9280

A bug in _ctfe branch that was introduced while stubbing out non-CTFeable blocks.
Now CTFE is having more power and able to run the same code just fine!
Fixup for cycle RangeError invocation

From: #1183 :
Issue 9612: Cycle opSlice should throw when finish > start

Because a RangeError is not actually customizable, and the first argument is actually the file name. The error was producing:
```
core.exception.RangeError@2 > 1(3836): Range violation
```

Now it produces:
```
core.exception.RangeError@std\range.d(3835): Range violation
```
Fix issue 4909
std.file: Make rename clobber on Windows, adjust docs (Issue 5032)
std.file: Document and test that copy clobbers
Merge pull request #1196 from monarchdodra/cycleFixup

Fixup for cycle RangeError invocation
Merge pull request #1194 from blackwhale/named-matches-fix

Fix a bug in CTFE branch of std.regex parser
Enable test lines that had been blocked by issue 2486