pdf of the manual runs certain long lines off into the right margin and beyond.
A fix forces a line break in an unusual way, and thus the pdf can be
fine wrt line breaks, but at the price of the html looking wrong.
Undo change in exit code checks for file transfer child processes. #4328

When a process created with Create_Thread() exits, we terminate the
process by exec'ing /bin/true or /bin/false. This means any non-zero
return value of the child is translated into the exit code of
/bin/false. On Solaris, this is 255, not 1.

For 8.0, we'll rely on the final status update to catch failures that
result in exiting with a non-zero status.
Terminate child "threads" with _exit() instead of exec(). #4332

We don't want processes created via Create_Thread() to execute C++
destructors when they exit. Both _exit() and exec("/bin/{true|false}")
can accomplish this. Using exec() means we only get a binary result of
zero/non-zero, and the non-zero value varies by platform. Using _exit()
gives us the full exit code range of values. With exec(), the parent
can't distinguish between a file transfer that succeeds and one that
calls EXCEPT().
Merge branch 'V8_0-branch' into V8_1_6-branch
Merge branch 'V8_1_6-branch'