syscall(): Make abort message visible

When syscall() was asked to perform an unknown syscall, we printed a
message with debug() and then called abort(). Since, recently, the message
from debug() is not visible on the console.

So pass the message directly to abort(), to do the right thing with it.

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Convert tst-epoll.cc to standard C++

Replace OSv-specific constructs in tst-epoll.cc by their standard C++
counterparts (i.e., std::thread, std::chrono, std::cout).
This test now also runs (and of course, succeeds) on Linux.

In general, it is important at all our Linux-ABI tests (where we test our
implementation of the Linux/glibc functionality) to be able to run on Linux
as well. Otherwise, it is possible our tests don't actually test the right
thing (we may test for some expected behavior, but the actual behavior on
Linux is different).

I'm doing this in preparation for fixing issue #188 (fix edge-triggered
epoll).

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
reclaimer: name reclaimer thread

Now we are showing names in gdb, it helps to name all of them.

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>