Add unittest to test collection of C sources and headers

reduce dependency on the working directory ...

Improves library API usage and bugs with the build generator

Unify reading and writing files under a single API ...

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.

Keep logging functionality out of the public API as requested in https://github.com/dlang/dub/pull/2124#issuecomment-813016939.

More improvements and replacements ...

Adapted generators output to new style, small change for non-selected
packages

New logging module - initial functionality ...

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

Generate paths relative to visuald project files (#2150) ...

Fixes #1477 : Internal paths for sources etc in projects should be relative to project file path. Actually relative to "working dir"/.dub

Actually copy copyFiles when building in Visual Studio. (#2105) ...

Actually copy copyFiles when building in Visual Studio.
merged-on-behalf-of: Max Haughton <maxhaton@users.noreply.github.com>

Include copyFiles and extraDependencyFiles in visuald projects. Resolves #1053.

If no output is generated (TargetType.none) then don't generate a project configuration. ...

This prevents VS from attempting to build a library with no name from no sources.
Fixes #2085.

betterC flag enabled in generated visuald project file. ...

Fixes #2024

Correct issue #1673 (with dupe #1797 and #2019)

Replace calls to NativePath.toString() with .name ...

This has been deprecated in vibe-core and only triggers with 'library-nonet'.

Remove some unused variables ...

There are plenty left, but those ones didn't seem to have any side effect.

Replace `hash_t` and `sizediff_t` with `size_t` and `ptrdiff_t`

Improve cross-compilation support (replace `version` checks by BuildPlatform runtime checks) ...

Also fixes #1249. For LDC as implicit cross compiler, the file
extensions for libraries and object files etc. don't depend on the
compiler, but solely on the target. Targets selected with `--arch` are
correctly probed by dub, so that the parsed `BuildPlatform` represents
the target platform.

Add support for DragonFlyBSD ...

- Switch from /bin/sh to /usr/bin/env bash
- Ignore temporary and test-build files (gitignore)
- Untrack changes to source/dub/version_.d
- Handling 'isDragonflybsd'
- Use 'tr -d' instead of 'tr --deleted' which works on Linux and BSD based platforms
- Fix FRONTEND = unbound variable (test/run-unittest.sh)

Fix compatibility with vibe.d < 0.8.2.

Rename Path to NativePath. ...

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

Make the code base compatible with vibe-core. ...

This still generates lots of deprecation warnings, but successfully compiles with vibe-core, as well as with the old vibe-d:core package.

Properly handle "x86_mscoff" pseudo architecture in the VisualD generator.

Avoid some uses of deprecated property Package.dependencies.

Move utility functions from dub.compilers.compiler to dub.compilers.utils.

Avoid any of the newly deprecated symbols. ...

The only exception is the serialization code, which still iterates over deprecated fields, as well as Package.dependencies, which will be replaced in the next commit.

Make all internal generator functionality private.

The VisualD project generator sets the working directory. Fixes #567.

Uses <debugworkingdir> to have the right debugging working directory.

Get .visualdproj files to be created in the .dub directory. Less cluttering of the working directory. ...

However this creates a problem since when debugging an executable through VS the default working directory will be .dub/ where it was ./ previously. This can cause eg. files not being found.

This "debugging working directory" setting is stored in the .suo file generated by the IDE, so maybe a VisualD option is needed to get out of this.

Change VisualD project generation logging. ...

- display the generate .sln filename which is usually the one you reach for after
- using the "solution" word instead of "project" since "projects" refers to parts of a solution in VS linguo.

Fix naming convention of FileMode enum. ...

Also some minor code style fixes.