Whitespace cleanup in root and 'build' folder.

* Removed trailing whitespace and empty lines at top of files.
Create packages_build folders per build type.

* The content of the preprocessed package-info files and the package
  contents depend on the build type, so we use a different folder for
  each build type.
Add new configuration option --no-downloads.

* If --no-downloads has been given, Haiku will be built without
  trying to download anything, all required packages need to be put
  into the download folder manually (the build will stop on missing
  packages).
* As the required HaikuPorts repository can't be downloaded in this
  mode, a local repository is created during the build, which only
  contains the packages available in the downloads folder.

This is useful for building Haiku completely from source.
Fix #10804: package_daemon crashing in Volume destructor.

* use delete [] for fPackagesDirectories, as it has been allocated
  via array new
radeon_hd: Don't squash ss status_t into bool
radeon_hd: Finish spread spectrum support

* This needs testing and is to remain disabled
  until we can test on several radeon_hd cards
  from multiple families
package daemon: Initial old packages state support

* VolumeState: Move locking to Volume.
* Package: Pull the file related functionality into new class
  PackageFile. A Package refers to a PackageFile. A PackageFile can be
  referenced by multiple Packages. PackageFiles are managed by the new
  PackageFileManager.
* CommitTransactionHandler: Clone the passed volume state.
* Volume now manages two VolumeStates: A state reflecting the currently
  active packages and the latest state (i.e. the one reflecting the
  situation of the packages directory). Usually the two are the same,
  unless an old state has been booted.
* The client interface hasn't been adjusted yet. Clients only see the
  latest state.
package daemon: Don't apply system package changes immediately

When a system package is going to be deactivated, activate/deactivate
the packages of the whole transaction only to the latest state.
Afterward latest state and active state will differ.
Add some links to the allwinner A10 docs.
Add HaikuWebkit 1.3.1.
Add libexecinfo.

This is a new WebKit dependency.
Minor cleanup: remove superfluous semicolon.
Improve build feature handling with HAIKU_NO_DOWNLOADS=1

* Adjust the respective rules such that with disabled downloads, only
  packages already available in the downloads folder will be considered
  as available build features.

This way, the build system will not for instance try to build
<kdebug>qrencode after a bootstrap, as that package is not yet
available.
Add variable noDownloads to build_haiku_image.

* If noDownloads is set, show an error when a download is requested.
BGradient: preserve order of stops with same offset.

* Use merge sort, which is a stable sort, instead of the qsort used in
BList::SortItems
* This allows setting two stops with the same offset to create a sharp
color change in a gradient. This trick is used to create stripe patterns
with css gradients in some web pages.

Fixes #10733.
Try to fix build on Linux.

* Linux is the only one of our supported build hosts to not have
mergesort. Provide an implementation that calls qsort, since the qsort
implementation in the glibc used by Linux uses a mergesort (!) for small
arrays.
Use std::stable_sort instead of mergesort.

* stable_sort is part of the C++ standard, and should work just as well.
Revert "Fix window behavior when default button is present"

With some testing, found that even with the second patch
provided in #10792, the behaviour is still inconsistent, so
reverting for now.

This reverts commit 273109e0048442ba5f6361d6e683e5b4a69a472b.
Update translations from Pootle