Include logic to engage Linden apr_procattr_autokill_set() extension: on
Windows, magic CreateProcess() flag must be pushed down into apr_proc_create()
level. When using an APR package without that extension, present
implementation should lock (e.g.) SLVoice.exe lifespan to viewer's on Windows
XP but probably won't on Windows 7: need magic flag on CreateProcess().
Using APR child-termination callback requires us to define state (e.g.
LLProcess::RUNNING). Take the opportunity to present Status, capturing state
and (if terminated) rc or signal number; but since most of the time all caller
really wants is to log the outcome, also present status string, encapsulating
logic to examine state and describe exited-with-rc vs. killed-by-signal.
New Status logic may report clearer results in the case of a Windows child
process killed by exception.
Clarify that static LLProcess::isRunning(handle) overload is only for use when
the original LLProcess object has been destroyed: really only for unit tests.
We necessarily retain our original platform-specific implementations for just
that one method. (Nonstatic isRunning() no longer calls static method.)
Clarify log output from llprocess_test.cpp in a couple places.