ResultItem: fix Coverity ID 700806 Uninitialized scalar field

In ResultItem::ResultItem(): Several scalar fields are not initialized
by the constructor.
MetadataLookup: fix Coverity ID 700886, 700885 Uninitialized scalar field

MetadataLookup::MetadataLookup(): Several scalar fields are not initialized by
the constructors.
fix Coverity ID 700887 Uninitialized scalar field

In ParentalLevelChangeCheckerPrivate::ParentalLevelChangeCheckerPrivate():
Several scalar fields are not initialized by the constructor.
VideoMetadata: fix Coverity ID  700888 Uninitialized pointer field

In VideoMetadata::SortKey::SortKey(): A pointer field is not initialized in
the constructor (false positive because it's a copy constructor so the field
will be copied anyway)
VideoMetadata: fix Coverity ID 700889 Uninitialized pointer field

In VideoMetadata::VideoMetadata(): A pointer field is not initialized in the
constructor (false positive because it's a copy constructor so the field will
be copied anyway)
fix Coverity IDs 746868, 700890 Uninitialized scalar/pointer field

In VideoScanner::VideoScanner(): A scalar field is not initialized by the
constructor.

In VideoScannerThread::VideoScannerThread(): A pointer field is not
initialized in the constructor.
fix Coverity IDs 700811,700812,700813,700814,700815 Uninitialized scalar fields
Fix GCC C++11 warning about narrowing conversion.
Use proper rpath syntax on OSX.
Add some copyright headers where missing.
Add more MythSystem unit tests.
Eliminate GetSignal() from new MythSystem.

The ability to query the signal that killed a program is not part of POSIX,
so we can't even depend on it on all unix systems. GetExitCode() will now
return -1 if a program was killed by a signal, -2 if it is still uncollected
and 0..255 if the program exited normally, so GetSignal() is unnecessary as
a call if all it tells us is whether a signal killed the program.
Eliminate dead MythSystem flag kMSBuffered.

IO is always buffered.
Add more MythSystem unit tests.
Add annotations to three flags to eliminate if possible.
Eliminate unused kMSInUi MythSystem mask
Eliminate unused kMSSetPGID MythSystem mask
Merge branch 'devel/mythsystem'
Update ABI version for MythSystem changes.
Fix significant leak of File Transfer sockets/threads