Deduplicate dflags and lflags ...

For some reason, dflags and lflags were not using the 'add' convenience function,
which allows to deduplicate flags.
As a result some flags, especially link flags which propagate upwards,
ended up taking half of the command line length.

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

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

extraDependencyFiles attribute added

infer unspecified version filters ...

- otherwise of little use as all dependencies need to have specified
  version filters before this can be used
- also version identifiers are fairly easy to grep for
- cache inferred version filters
- still allows explicit specification for packages that use version
  identifiers in mixins

Added experimental build settings to filter applicable version identifiers ...

Those settings allow to filter version identifiers and debug version identifiers
used during building a package. This can improve the build cache efficiency for
libraries that are used by multiple applications with different version
identifiers.

- only merge filters from source dependencies when the
  dependent has an explicit filter list as well

Pre/post run commands added

Add betterC build option

Fix buildsettings.d according to Sebastian Wilzbach notes ...

Style, NativePath memoizing, more refactoring

See https://github.com/dlang/dub/pull/1335 for details

buildsettings.d refactored to more std library usage

Rename Path to NativePath. ...

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

Remove compatibility code for DMD frontends < 2.067.x.

add tests for BuildSettings add/remove functions ...

- also convert them to static functions and use a single `private:` attribute

make pic inherited for dynamic libraries

replace slow O(N^2) removeImportFiles with set difference ...

- dub build for a vibe-d project w/o changes (300ms -> 100ms)

Avoid cubic runtime for collecting files. Fixes #1690. ...

This is still not very efficient, but now has a finite runtime for large numbers of files.

prepend defaultlib on dmd

Remove deprecated functionality to prepare for 1.0.0.

Mention version of removal for all deprecated public symbols.

Fix all deprecation warnings on 2.071.0-b1, except for std.stream. ...

std.stream is still needed to support UTF filenames.

fix gdc/ldc flags for ddox/docs ...

- it seems that gdc cannot currently generate a
  single json file with all output though
- remove dummy doc files after as postBuildStep

Don't pass -unittest to dependencies when performing a test build. Fixes #640.

add buildType profile-gc ...

- allows to dub build -b profile-gc to
  trace memory allocations with dmd

Again, rework --data's handling of sourceFiles and static library dependencies.

Rework --data's handling of sourceFiles and static library dependencies.

Split --data=libs into two: --data=libs (for installed/system libs) and --data=lib-files (for dependency libs) ...

This is needed because compilers/linkers often expect the two types of libs to be passed in differently: System/installed libs (--data=libs) must be provided like "-Lname" which the linker automatically converts to "path/lib*.a". Non-installed libs, such as dub dependencies, are passed with full filepath just like an object file. Your linker may vary.

Add "targets" field to "dub describe" output.

Change Build(Options/Requirements) to BitFlags.

Avoid adding duplicate string imports in BuildSettings.addStringImportFiles. ...

Prepares for fixing #331.

Fixed issue where static libraries would be generated instead of object files in singleFile build mode ...

+ Added object TargetType that is used during singleFile build mode

Put BuildSettings into its own module and invoke DMD to determine the actual build platform. ...

Currently only for DMD, the build platform is now determined by actually invoking the compiler with the proper -mX switches instead of guessing from the compiler run that was used to build DUB.