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.

Remove "_d suffix for "debug" builds in VisualD generated project files. ...

The problem is that it is inconsistent with how "dub build" work.
Also (this is opinion here) it lets output files proliferate with little benefit.

Change Build(Options/Requirements) to BitFlags.

Remove some obsolete code.

Apply patch by ketmar: remove comma expressions and fix property syntax. ...

Also contains two minor additional style fixes.

Added @property at MartinNowak's request

Broke long line onto multiple lines

Reamed vsCpuArchitecture to vsArchitecture ...

- Moved to end of module and made private similar to existing utility
functions
- Cleaned up spaces instead of tabs

Fixed generation of Solution Platform for x64

Remove PackageManager argument from createProjectGenerator(). ...

The argument is also removed from all Generator sub classes.

Step one of abstracting package description format

Added singleFile support

Removed trailing whitespace

Converted line endings from CRLF to LF

Fix orphan format specifier.