Update qore to version 0.8.11.
Removed devel/libexecinfo buildlink because I belive this might cause
problems when building under smartos.

Release notes:

Release Summary
 Minor bugfix release for UNIX, major bugfixes for Windows

New Features in Qore

 added the Qore::AFMap and Qore::AFStrMap constants

 WebUtil updates:
    added logic to the default file serving code to determine if the
    file is a binary or text file from the MIME type

 HTTPClient::sendWithSendCallback() and
 HTTPClient::sendWithSendCallback() updated such that if a response is
 received while the chunked send operation is still in progress, an
 error is assumed, the send operation is aborted, and the response header is
 read immediately

Bug Fixes in Qore

 Windows fixes:

    fixed TimeZone copying to use the standard name instead of the
    display name so that the info can be found in the registry

    Util module fixes:
      fixed get_random_string() on Windows
      fixed absolute_path_windows()

    HttpServer module fixes:
      when binding a wildcard address with AF_UNSPEC on Windows with
      HttpServer::addListeners() and both IPv6 and IPv4 addresses are
      returned, bind both addresses since Windows doesn't direct the
      IPv4 requests to the wildcard-bound IPv6 listener

    fixed file reading by always opening in binary mode

    added support for the WSAECONNABORTED socket error

    replaced Mime::MultiPartMessage::getRandomString() with

    Util::get_random_string() to make it work on Windows

 fixed a bug in the DBI layer where calling SQLStatement::describe()
 would crash when called with an older module that did not implement
 this method

 other fixes in the Util module (in addition to the Windows-specific
 fixes above):

    fixed parse_to_qore_value() with hashes with a comma in the first
    key name

    read from /dev/urandom instead of /dev/random since reads from the
    latter can block for long periods to fill the entropy pool

 do not start signal thread after a fork() if signal handling is
 enabled, pthread_create() is not async-signal safe (on FreeBSD at least
 this reliably causes segfaults)