Use JobObject to optionally terminate spawned process tree

[shinfd]

When the service is requested to stop from the management console or via sc stop command, current implementation of srvany-ng does not terminate any descendant processes spawned by the service application.

This is in line with the original srvany, as documented in the below article:

Q&A: Why doesn’t Srvany Close my Application when I Stop the Service? | | The Core Technologies Blog

Still, I thought it would be great if support for process tree termination could be added.

Using Job Objects seems to be most straightforward, so I am sending this PR as a suggestion.

The default behavior is unchanged. Please add and set UseJobObject DWORD registry parameter to 1 to enable the new behavior.

Note: As written in MS' reference, Job Objects has limitation before Win 8 and Windows Server 2012.

Windows 7, Windows Server 2008 R2, Windows XP with SP3, Windows Server 2008, Windows Vista and Windows Server 2003: A process can be associated with only one job. Jobs cannot be nested. The ability to nest jobs was added in Windows 8 and Windows Server 2012.

So using Job Object in srvany-ng may clash with program already using Job Objects, when running in older environment; hence the optional implementation.

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Some things that may need to be addressed / discussed:

• Current implementation does not clean up event handle created here on error exit
  • Followed existing pattern (1/2) for PR commit , and could not tell if these all should be changed
• UseJobObject may not really convey what it performs and may not be appropriate for registry key
• If PR were to be accepted, README needs to mention the new registry parameter