Simplified os::hostname() in libstout.

Review: https://reviews.apache.org/r/11108
Shuffle offers before sending to frameworks.

This helps ensure fair allocation of resources.

Review: https://reviews.apache.org/r/11121
Added --enable-debug configure flag.

Review: https://reviews.apache.org/r/11605
Slave ping timeout may be increased by flags.

Review: https://reviews.apache.org/r/12885
Turned down noise from ZooKeeper.

Review: https://reviews.apache.org/r/11127
Use hostname instead of IP for redirection.

In the Web UI, the redirection does not work for hosts where the local
interface address is not publicly accessible.  For example, with EC2 the
redirection will not work.

This change writes the Master's hostname into ZooKeeper, thereby
allowing the redirection to work with private IP addresses.

Review: https://reviews.apache.org/r/11975/
On recovery fail, do rm -rf /tmp/mesos/meta.
Use libstout cache for slave completedFrameworks.

The list of retired (completed) frameworks is now a stout cache rather
than a boost circular buffer.  There are now key iterator accessors for
the cache class, and a removal member.

Review: https://reviews.apache.org/r/13599
Added a slave load hint for scheduler sorting.

With this change, the offers will include a slave load hint based on the
5 minute load average for that slave (returned from getloadavg()).
Frameworks can use this hint to select among otherwise similar offers,
as an optimization.

Review: https://reviews.apache.org/r/13675
Increase web UI reload delay.
Fixed some task reconciliation cases.

Case 1:

If a slave is known but the task cannot be found, we should assume that
the task has been lost.  It's possible that the following events
occurred:

 1) Framework disconnected from master
 2) Master terminated framework's tasks
 3) Framework reconnects to master, and (incorrectly) assumes tasks are
 still running

Case 2:

If a framework loses track of running tasks, the master should inform
the framework of which tasks it knows to be running, in addition to any
which have had a state change.

Review: https://reviews.apache.org/r/15745
Fixed an exception raised in the master related to task statuses.

Review: https://reviews.apache.org/r/16038
Fix for a5c4eba5c56e2.
Attempt to kill more gracefully.
Fixed protobuf::read bug exposed when running Mesos compiled by clang.

Review: https://reviews.apache.org/r/16660
Bug in http::request missing os::close.

Review: https://reviews.apache.org/r/17093

Conflicts:
	3rdparty/libprocess/src/process.cpp
Fixed slave to properly do memory isolation when executor resources
are not specified.

From: Vinod Kone <vinodkone@gmail.com>
Review: https://reviews.apache.org/r/17295
Enhanced DRF by including past allocations.

The DRF allocator (master/drf_sorter.hpp|cpp) currently only uses a
framework's share to determine an ordering for allocating
resources. When there are very few resources to go around it's
possible that a framework will get allocated resources (making it have
a dominant share larger than others), use those resources, then return
those resources (making it's dominant share equal to the share of
others), and then get reallocated the resources _again_ because its
dominant share is equal to others. This can cause starvation for
frameworks.

Review: https://reviews.apache.org/r/19090
Fixed overcommittal bug in recovery.

If a task attempts to use more than the available resources at recovery,
terminate it.