cloudstack: implement general api_region support, update docs

Fixes #12018

TODO: add this to VariableManager to validate vars loaded from files too

Fixes #12022

Update "smart" transport to handle Sun_SSH_1.5 on SmartOS

Link to `constants.py` in the source tree from the documenation.

Python 3: use print() as function under contrib/

`constants.py` is referenced in the *Environmental configuration* section of the documentation.  This change provides a link from the documentation to the source code.

This fixes the remaining Python 3 syntax errors, so re-enable compileall
for contrib/ again.

- Fixed line break causing part of the text to display as "Definition List"  which Sphinx renders in bold.

  which Sphinx renders in bold.

fixes #12111

Adding support for Archlinux and Slackware in fallback

Enable py34 test in travis so we don't regress recent fixes

Some steps towards Python 3 support

`assert (condition, message)` gets parsed by Python as `assert
a_two_tuple`, and a 2-element tuple is never False.

Discovered by compileall on Python 3.4, which emits a SyntaxWarning for
this common mistake.

(This is supposed to be temporary, until the code under contrib/ gets
cleaned up from all the remaining print statements.)

You cannot call bytes(obj) to get a simple representation of obj on
Python 3!  E.g. bytes(42) returns a byte string with 42 NUL characters
instead of b'42'.

types.NoneType was removed in Python 3.

None is a singleton in Python, so 'x is None' is equivalent to
'isinstance(x, NoneType)'.

I neglected the __future__ import because

  print(one_thing)

works the same way even when print is a statement.

Python has had automatic int-to-long promotion for a long long time now.
Even Python 2.4 does that automatically.

Python 3 drops support for the L suffix altogether.

This syntax is valid in Python 2.6+ and 3.x.

It's not allowed in Python 3 and merely a bad idea in Python 2.

This syntax works on Python 2.6 through 3.x.  lib/ansible/module_utils
(and lib/ansible/modules) need to support Python 2.4, so I didn't touch
those.

Implement cat-like filtering behaviour for encrypt/decrypt

Add hash_merge and hash_merge_recursive filters with documentation

This is based on some code from (closed) PR #7872, but reworked based on
suggestions by @abadger and the other core team members.

Closes #7872 by @darkk (hash_merge/hash_replace filters)
Closes #11153 by @telbizov (merged_dicts lookup plugin)

Don't compile .py files under .tox/

Remove deprecated and unused VaultAES encryption code