all: starting development of 2.6.4
lib: internal: worker: snapshots: renameSnapshot: don't accept invalid snapshot names
lib: internal: worker: snapshots: snapshot names having whitespace characters are invalid
lib: internal: worker: snapshots: renameSnapshot: refactoring: removed the part already done by by 'checkSnapshotName'
lib: internal: exceptionlessfuture: initial implementation
lib: internal: worker: metadata: p_runMetadataUpdateThreads: use 'ExceptionlessFuture' instead of 'std::future'
debian: control: bumped Standards-Version to 3.9.5
all: 2.6.4 release
lib: internal: worker: packages: writeOutConfiguration: print 'APT::Architecture' option case-sensitively
lib: internal: worker: packages: support VERSION 3 of preinstall hooks
lib: file: mark destructor as noexcept(false) explicitly

Since version 4.8 g++ learned to mark all destructor as noexcept(true)
by default. This caused any exception which leaves a destructor
uncatched invoke std::terminate() immediately.

In File class, we do want exceptions to leave the constructor, thus mark
them as so explicitly.
lib: internal: pipe: added a flag to keep reader part open after exec()
lib: internal: worker: base: _run_external_command: support for directing command input onto specified file descriptor
lib: internal: worker: packages: p_getCommandInputForPreinstallPackagesHook: support for hook's infofd setting
Merge branch 'fixes/2.6'