mkdirRecurse will not do anything if the directory already exists,
so there is no need to call existsDirectory.

As it is not available on all platforms, we can't really rely
on it for code, and it is indeed not used anywhere.

This reduces the number of deprecations issued in dub.

In practice we only every iterate directories in a foreach,
which means iterateDirectory is the only function ever used.

It was actually unused, because al the call sites were doing a useless
round-trip from NativePath to string to NativePath.
There is no need for it anymore so we can just remove it to avoid
this kind of mistakes in the future.

All usages actually want to ensure the directory is present,
and don't care about having a separation between existence check
and creation.

It doesn't make sense to have those in two separate modules.

This removes the range API and instead uses Appender,
while using a limited and centralized set of functions
to read/write from files.
The end goal is to permit dependency injection,
which is a pre-requisite to extending the test-suite.

We don't actually use URL here, nor should we,
we use path, so correct the import.

The new module replaces dub.internal.vibecompat.core.log by using the
same function names, but implementing colored output and the left
fixed-width tag. Overloaded functions are provided to output colored
text.

Still missing initLogging() and non-TTY stdout/stderr detection

Matches the changes done in vibe.d 0.8.x and vibe-core.

Since `std.file.copy` provides a means to preserve attributes of a file
as of DMD 2.067.0 or later, it is preferable to use this option rather
than having a custom-written solution.  `version (Posix)` special-casing
is therefore used only where the DMD version does not support it.

Note that where the `version (Posix)` code uses a `chown` call followed
by a `chmod` call, `std.file.copy` only uses a `chmod`.  This is not
expected to cause any issues but should be borne in mind as a possible
breaking change for some use-cases.

Fixes https://github.com/dlang/dub/issues/992.

Since opening non-ASCII filenames on Windows is fixed for the latest DMD version, it now only has to be made sure to use a recent compiler to build DUB.

Also some minor code style fixes.

hardlink files into target dir

- fixes Issue #457 - stale symlinks

- also thisExePath will now point to the target binary

- also implemented on Windows

- fallback to copy

Also contains two minor additional style fixes.