[nicolas-grekas]

Related to bug #38480 and to #22538.

With pcntl_async_signals(true), signal handlers now run while time_sleep_until() waits. A handler can throw or exit before the deadline. If the handler returns, the sleep resumes until the original deadline.

#24399 already made the sleep resume with the remaining time. This PR adds the missing part. When nanosleep() is interrupted, time_sleep_until() now calls zend_fcall_interrupt(), like the VM does after an internal function returns. As a consequence, max_execution_time can also stop the sleep when its timer interrupts nanosleep().

A signal that arrives while another handler is running still waits for the deadline, because pcntl blocks signals during a handler.

[nicolas-grekas]

Rebased. #24399 already merged the part that resumes the sleep, so this PR is now 6 lines plus tests. I added a test for the sleep resuming after a handler returns, and I updated the description.

@arnaud-lb WDYT of this as a first step before #22538 reaches the other EINTR loops? There's one difference with #22538. Here the sleep always resumes when the handler returns, whatever $restart_syscalls says.