put version filtering behind an experimental switch

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

add main source files to root executable earlier

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

fix unix executables gitignore

Merge pull request #1582 from andre2007/feature_pre_post_run_command ...

Pre/post run commands added
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Merge pull request #1590 from andre2007/fix_issue_1136 ...

Fix temp copy files
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Merge pull request #1594 from Flying-Toast/update-gitignore ...

Ignore unix executables in generated .gitignore
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

remove unneeded /

gitignore unix executables

Merge pull request #1526 from andre2007/fix_issue_1524 ...

Late dependencies resolver
merged-on-behalf-of: Jan Jurzitza <gh@webfreak.org>

Retry download for registry search packages

Merge pull request #1481 from SimonN/issue1478-quote-xcopy ...

Fix #1478 - Quote paths passed to xcopy

Fix temp copy files

Pre/post run commands added

Use default architecture for ddox

Fix #1478 - Quote paths passed to xcopy ...

On Windows, `cd` accepts unquoted paths, but for any calls to `xcopy`,
paths arguments must be double-quoted. This patch surrounds all paths
with double-quotes before passing them to `xcopy`.

This fixes #1478: On Wine (and presumably Windows XP), migrating the dub
package directory from dub 1.7 to dub 1.8/1.9 via `xcopy` failed an
enforce in dub (because `xcopy` quit with nonzero exit code) and thus
prevented even the most simple dub projects from being built.

D WYSIWYG strings (backtick-surrounded strings) allow all characters
unescaped, including double quotes and backslashes.

Merge remote-tracking branch 'upstream/stable' into merge_stable

update version to v1.12.0

Maven upgrade dependency tree

Merge remote-tracking branch 'upstream/stable' into merge_stable

update version to v1.12.0-rc.1

Merge remote-tracking branch 'upstream/stable' into merge_stable

update version to v1.12.0-beta.2

Fix Issue #1504 ...

Avoid reusing forward ranges.

Add test for Issue 1504

Make test issue1504-envvar-in-path executable

Fix test Issue 1504

Add .no_test to hopefully fix test1504

Added .no_build
Removed .no_test

Test should work now.

Fix test, for good? All bets are off.

Merge pull request #1580 from dlang/revert-1532-min_dub_version ...

Revert "implement "minDubVersion" field"

Revert "implement "minDubVersion" field"

Merge pull request #1576 from MartinNowak/merge_stable ...

Merge remote-tracking branch 'upstream/stable' into merge_stable
merged-on-behalf-of: Petar Kirov <ZombineDev@users.noreply.github.com>

Merge pull request #1566 from andre2007/fix_refactor_retry_download ...

Refactor retry download

Merge pull request #1552 from Geod24/fix-single ...

Fix #1551: Escaping a variable ($$) is ignored