Problem: qt-android build doesn't fully work for downstream builds

Solution: Fix the qt-android build

Restore structure to targets lost during nonrecursive refactor.

Problem: No builtin way to build for qt-android

Solution: Don't print tar extraction verbosely

Solution: Add qt-android build system and add to travis-ci

Disable IPC testing on ipc-incapable systems in test_term_endpoint.cpp

Added test and updated documentation for unbind wild-card * binded socke...

Unbind socket with real endpoint when binding by wild-card * address

Support both --enable-eventfd and --disable-eventfd options.

Pass --with/--without-libgssapi_krb5 to configure.

Standardize optional libgssapi_krb5 dependency

Fix issue #1224

Improve build script error checking.

This commit adds a check to make sure pkg-config is present on the
computer building libzmq.
This particular line was stolen from the debian mailing list.
See https://lists.debian.org/debian-dpkg/2011/04/msg00054.html

Revert "ZMQ API diverges from POSIX"

ZMQ API diverges from POSIX

Update travis script to configure with libsodium.

Support --with and --without options for libsodium and pgm

command line options.

Append to libzmq_la_CPPFLAGS and libzmq_la_LIBADD.

Remove build and runtime dependencies on e2fsprogs and e2fsprogs-devel.

Add support for POLLPRI flag.

This commit adds a ZMQ_POLLPRI flag that maps to poll()'s POLLPRI
flag.
This flags does nothing for OMQ sockets. It's only useful for raw
file descriptor (be it socket or file).
This flag does nothing if poll() is not the underlying polling
function. So it is Linux only.

Releasing 4.1.0 rc1 and moving development master to 4.2.0.