Properly qualify process::Failure() in posix.hpp.

Fixed compilation problems when compiling files which include
<slave/containerizer/isolators/posix.hpp> without
"using process::Failure".

Review: https://reviews.apache.org/r/26791
Added "name" to Modules protobuf.

Allow the users to specify a bare library names.

For example, "foo-2.3" will expand to "libfoo-2.3.so" on Linux and
"libfoo-2.3.dylib" on OS X.

Review: https://reviews.apache.org/r/26674
Allowed unloading of a single module.

unloadAll() forces destruction of Owned pointers to the dynamic
library handle. This implicitly causes a dlclose() of all the loaded
module libraries. Unloading a dynamic library can have side effects if
some shared state (e.g., a module) in Mesos points into the library.

Futher more, removed the existing unloadAll() that is no longer
needed.

Review: https://reviews.apache.org/r/26789
Added an advisory message reminding the user to initialize the log.

Review: https://reviews.apache.org/r/26815
Fixed a typo in the last commit.
Supported O_CLOEXEC for os::open on all platforms.

Review: https://reviews.apache.org/r/26715
Added a protobuf::append function.

Review: https://reviews.apache.org/r/26799
Added a protobuf::append test.

Review: https://reviews.apache.org/r/26800
Added the missing --path to the replicated log advisory message.
Fixed verify-reviews.py to not apply submitted reviews.

Review: https://reviews.apache.org/r/26827
 Temporarily disabled Module tests due to MESOS-1942.
Escaped JSON object keys.

All strings in JSON need to be escaped, including the keys in
dictionaries / objects.

Review: https://reviews.apache.org/r/26723
Refactored stout os open/close/fcntl.

Review: https://reviews.apache.org/r/26843
Updated verify_reviews.py to use the git pre-commit hook.

Review: https://reviews.apache.org/r/26798
Renamed verify-reviews.py to verify_reviews.py.
Fixed default port values for master and slave in the documentation.

Review: https://reviews.apache.org/r/26254
Fixed a file descriptor leak in StatusUpdateManager.

Review: https://reviews.apache.org/r/26879
Fixed MESOS-947: Slave should properly handle a killTask() that arrives
between runTask() and _runTask().
Temporarily disabled KillTaskBetweenRunTaskPart test due to MESOS-1945.
Fixed ZooKeeper 3.4.5 OSX Yosemite build.

Fixes build issue caused by htonll introduced by OSX 10.10 (Yosemite).

This poses as a hotfix to prevent us from having to upgrade the bundled
ZooKeeper altogether to prevent longer regression testing. Once
ZooKeeper does get updated into a recent version (3.4.x >= 3.4.7,
3.5.x >= 3.5.1 or >= 3.6.0), this patch should get removed.

Review: https://reviews.apache.org/r/26571