Additions/VBoxService: when starting guest processes, ignore VERR_INTERRUPTED when reporting the status to the host because SIGCHLD might be triggered by a very fast child which already terminated at this point

Guest Control: - Implemented IGuestSession::DirectoryRemove, IGuestSession::DirectoryRemoveRecursive, IGuestSession::DirectoryRename + IGuestSession::FileRename. - Added appropriate commands to VBoxManage (basic support for now). - Implemented support for proper guest session process termination via SCM. - Implemented support for internal anonymous wait events which are not relying on the public API's VBoxEventType_T. - Various bugfixes.

Additions/GuestCtrl: Use a separate filter mask + value for message filtering.

VBoxService/GuestCtrl: More message filtering for guest session + process threads; message processing not needed there, logging.

VBoxService/GuestCtrl: Re-added (optional debug) dumping of guest process streams, now as a (forked) per-session option.

VBoxService/GuestCtrl: Implemented asynchronous request queue, bugfixes.

VBoxService/VBoxServiceControlProcess: Also report process termination status when started as detached.

VBoxService/GuestCtrl: Don't hang on PID reuse.

Format string: RU32 -> RU64.

VBoxService/GuestCtrl: Forward ported r87539 + r87613 (4.2: VBoxService/VBoxServiceControlThread: (Another) fix for guest process timeout / pipe handling.).

Forward ported / integrated r86363 (4.2: VBoxService/sysprep: Fixed slashes, more logging about looking up executable. Print warning when trying to execute sysprep on 64-bit OSes with 32-bit service executable).

Additions/VBoxService: Don't use VBOX_WITH_PAGE_SHARING here as this is a global defined symbol (VBox/param.h). Fixed warning.

GuestCtrl: Various bugfixes required for test driver to pass.

VBoxService/GuestCtrl: Also check for stopped state before performing a request.

VBoxService/GuestCtrl: Added asynchronous request handling, more fixes for testcases.

GuestCtrl: Implemented using (public) VirtualBox events instead of own callback mechanisms. Bugfixes for testcases (still work in progress).

GuestCtrl: More stuff for IGuestFile and IGuestSession handling (work in progress).

VBoxService: Renamed VBoxServiceControlThread.cpp -> VBoxServiceControlProcess.cpp.