devel/nspr's self-test failing: `mutex is on list'

[Mikhail Teterin]

Unfortunately, the tests are not being run automatically every time the port
builds, so we don't know, when the problem began...

To reproduce:

	% cd /usr/ports/devel/nspr
	% make build test

[...]
        forktest                        FAILED
        forktest:       Wait one second before accept
        forktest:       Wait one second before connect
        forktest:       Connecting to port 51686
        forktest:       Writing message "Hello world!"
        forktest:       Accepting connection at port 51686
        forktest:       Received "Hello world!" from the client
        forktest:       The message is received correctly
        forktest:       Fork succeeded.  Parent process continues.
        forktest:       Wait one second before accept
        forktest:       Wait one second before connect
        forktest:       Fatal error 'mutex is on list' at line 540 in file /usr/src/lib/libpthread/thread/thr_mutex.c (errno = 43)
        forktest:       Fork succeeded.  Child process continues.
        forktest:       Accepting connection at port 56714
        forktest:       Connecting to port 56714
        forktest:       Writing message "Hello world!"
        forktest:       Received "Hello world!" from the client
        forktest:       The message is received correctly
        forktest:       Parent process exits.
        forktest:       FAILED
[...]

I'm unsure, whether the bug is in the test itself or in the pthread,
or in the nspr-library's threading implementation, but the test used
to pass...

Would a thread-expert care to investigate, please? Thanks!

	-mi