openssl: Report correct key length for EC keys when not using NIST curves

Fixes #688.
unit-tests: Add option to exclude specific test suites

Listing test suites in TESTS_SUITES_EXCLUDE allows excluding specific
test suites from running.
curl: Log error code too

It seems libcurl does not always return an error message.
mutex: Use atomics to set current thread in recursive mutex

Because this->thread is also read by threads that don't hold the
mutex the previous implementation was problematic (especially since
pthread_t is an opaque type of unknown length).

Fixes #654.
swanctl: Document how connections.*.unique affects initiators
kernel-pfkey: Report packet counts of IPsec SAs

Seems that packet counts can be retrieved after all. At least the Linux
and FreeBSD kernels treat the number of allocations as number of packets.
We actually installed packet limits in that field already.
ip-packet: Define our own structs to handle TCP/UDP headers
kernel-pfroute: Delete interfaces on RTM_IFANNOUNCE/IFAN_DEPARTURE events

We actually never deleted cached interfaces.  So if the kernel reuses
interface indices events for newly created interfaces could have been
associated with interface objects of deactivated and deleted interfaces.

Since we also didn't update the interface name when such an interface
got reactivated we ended up using the old name e.g. to install routes.

A trigger for this was the deletion and recreation of TUN devices during
reauthentication of SAs that use virtual IPs.
asn1: Make sure not to exceed buffer for binary OID
ike: Reset IKE_SA in state CONNECTING instead of reauthenticating

Due to how reauthentication works for IKEv1 we could get a second
IKE_SA, which might cause problems, when connectivity problems arise
when the connection is initially established.

Fixes #670.
ikev1: Make sure proposed IPsec mode matches our own

References #557.
eap-radius: Forward Cisco and Microsoft specific DNS/NBNS attributes

Fixes #677.
android: Add support for querying use stats of a CHILD_SA
stream-service: Restart accepting without blocking

Calling on_accept() sometimes lead to deadlocks when service->destroy()
was called concurrently.  That is, two threads waiting in on_accept() but
the last worker would only wake one due to the call to signal().  Calling
broadcast() wouldn't help either as that could lead to crashes if the thread
that called destroy() is woken first.

This is also more efficient as a constant pool of concurrent workers can
be maintained, otherwise peaks at the limit were followed by only a single
worker being active.
stream-service: Do not accept or re-register when service is terminated
stream-service: Prevent race conditions due to blocking call to destroy()

In the previous implementation queued jobs could prevent a service from
getting destroyed.  This could have lead to a deadlock when the
processor is cancelled.  Now destroy() still blocks, but waits only for
actually running tasks.  The service instance is reference counted so that
queued jobs can safely be destroyed.
unit-tests: Give worker threads time to clean up when testing thread_t.detach()
asn1: Try to fill the available binary OID buffer if possible
array: Warn about caveat with array_remove_at() and value based arrays

Because enumerate() for value based arrays returns a pointer directly to
the internal array elements and because array_remove_at() or rather the
called array_remove() may move elements over the element at the currently
enumerated position, the pointer passed to enumerate() will point to a
different array element after the array_remove_at() call.  The caller
will thus operate on the wrong element if that pointer is accessed again
before calling enumerate().

For performance reasons we currently don't change the implementation to copy
each array element during enumeration to a private member of the enumerator and
return a pointer to that.  Similarly, due to the danger of subtle bugs we don't
remember the pointer passed to enumerate() to later redirect it to a copy
created during the array_remove_at() call.
array: Adjust negative index before calling remove_head|tail()

For ARRAY_TAIL we most often want to call remove_tail() not remove_head().