Switch [stout] to using compiler intrinsics for unreachable, exit, and abort

Use compiler intrinsics for unreachable, exit, and abort
Makes the functions not need to pretend to return something while
still silencing the compiler warnings.

Replaces 25191 (I originally authored the patch, but Patrick was managing it for various reasons). Incorporates the fix suggested by Ben Mahler. Fixes Dominic's build issue.

Review: https://reviews.apache.org/r/26100
Switch [libprocess] to using compiler intrinsics for unreachable, exit, and abort

Use compiler intrinsics for unreachable, exit, and abort
Makes the functions not need to pretend to return something while
still silencing the compiler warnings.

Replaces 25192

Review: https://reviews.apache.org/r/26101
Switch [mesos] to using compiler intrinsics for unreachable, exit, and abort

Use compiler intrinsics for unreachable, exit, and abort
Makes the functions not need to pretend to return something while
still silencing the compiler warnings.

Replaces 25193

Review: https://reviews.apache.org/r/26103
Fixed AllocatorTest.FrameworkExited test.

Review: https://reviews.apache.org/r/26144
Remove depreacted webui_hostname and webui_port fields from SlaveInfo.

These have been deprecated since November 2013, at least Mesos 0.16.
Should be safe to remove at this point (People will have to upgrade
pre-0.16 to something between 0.16 and 0.20.1 inclusive, before
upgrading past 0.20.1).

Review: https://reviews.apache.org/r/26149
Remove unused tuples folder.

Review: https://reviews.apache.org/r/26152
Fixed AllocatorTest.SlaveLost test.

Review: https://reviews.apache.org/r/26163
Updated documentation/flags regarding new default hostname semantics.

Review: https://reviews.apache.org/r/26185
Synced container network configurations with host network
configurations.

Review: https://reviews.apache.org/r/26197
Changed routing diagnosis socket state from enum to int so that they can
be bitwiseor'ed together.

Review: https://reviews.apache.org/r/26236
Included a missing header file in src/Makefile.am.
Fixed the flaky SlaveRecoverTest.MultipleSlaves.

Review: https://reviews.apache.org/r/26243
Switched path::join() to be variadic

Review: https://reviews.apache.org/r/25818
MESOS-1857 Fixed path::join() on older libstdc++ which lack back().

Review: https://reviews.apache.org/r/26256
Added webui_url to FrameworkInfo and web UI.

Allows frameworks to register a URL to its web UI.

Review: https://reviews.apache.org/r/26125
Replace some asserts with CHECKs in dispatch.

Review:
Added TCP RTT statistics for port mapping network isolator.

Review: https://reviews.apache.org/r/26090
Converted diagnosis socket Info to a struct.

Review: https://reviews.apache.org/r/26290
Moved Mesos version from mesos.hpp to version.hpp.

This allows the Module subsystem to simply include <mesos/version.hpp>
instead of inheriting the whole protobuf header chain.

Review: https://reviews.apache.org/r/26303
Install Python libraries during make install.

Because eggs are impossible to uninstall, pip + wheel has been added
as a packaging format. The wheels are generated in addition to eggs
and then subsequently installed/uninstalled.

Note that the building of eggs has not been removed. This is because
wheels cannot be run in place like eggs are via. modification of
PYTHONPATH. The eggs are needed for all the test scripts to run
correctly without actually installing anything locally.

Review: https://reviews.apache.org/r/24264