Switched min_heap to size_t to prevent integer overflows.

Also, as deraadt suggested, switched realloc to recallocarray to at least
prevent uninitialized memory to be used as pointers in case of other
programming errors. A proper solution (not using an array) needs more work.

This change occured in sync with upstream libevent 2.2.

with input by and ok bluhm, jca, tedu

knf, ok bluhm

unfold some compound operations to make this easier to follow

After removing all the #ifdef, the wrappers in evutil are rather
useless. Let libevent call the libc functions directly.
OK nicm@

Update to 1.4.14b.

From their change log:
o Fix memory-leak of signal handler array with kqueue. [backport]
o Make evutil_make_socket_nonblocking() leave any other flags alone.
o Adjusted fcntl() retval comparison on evutil_make_socket_nonblocking().
o Re-add event_siglcb; some old code _was_ still using it. :(
o Fix a free(NULL) in min_heap.h
o Clean up properly when adding a signal handler fails.

Also a local change to use an int rather than a long for fcntl().

ok guenther deraadt

Update libevent to 1.4.13.

This is the core library only, the DNS parts are removed and it does not
include the other extra bits (HTTP, DNS, and RPC), a separate port for
these will appear in due course.

Thanks to jsg, sthen, alek, gilles, jacekm, bernd and any others I've
forgotten for testing/comments.

Note that /usr/include/evdns.h should be removed after updating.

ok deraadt