Prevent stager deadlock if inp/out detection hangs for some reason

Even though there are calls to has_read_data(), it doesn't prevent
the put() call from blocking in a dead client or slowaris-like
situation. By moving the inp/out detection into the thread, we
allow the main handler to keep processing connections even if
a single connection hangs.
Add ReverseListenerThreaded option to prevent deadlocks

JodaZ reported that the handle_connection() sock.put call can
result in the entire reverse_tcp stager hanging if the client
stops receiving or is on a very slow link. The solution emulates
what ReverseTcpDouble already does, which is stage each connection
in a new thread. However, given that a high number of threads
can be a problem on some operating systems (*ahem* win32) this
option is not enabled by default.

We should look into thread pooling and handle_connection() timeouts
as well as event-based polling of multiple clients as alternatives,
but this option will improve the situation for our existing users.
Remove redundant option (threads are always used in reverse_tcp_double)
Identify the hung host in the thread info
Modify get_cookies regular expression
Add spec for comma separated cookies
Add new Yokogawa SCADA exploit
Land #3499, Yokogawa's CVE-2014-3888 module
Description/whitespace changes (minor)

Four modules updated for the weekly release with minor cosmetic fixes.

- [ ] See all affected modules still load.
- [ ] See all affected modules have expected `info`
Merge pull request #3500 from todb-r7/fixup-release

Release fixup: Description/whitespace changes (minor)
Land #3497, comma-separated get_cookies
Fix Meterpreter PHP hop description
Land #3509, Meterpreter PHP hop description fix
Make merged module descriptions more grammar.
Switch to a space. It gets eaten anyway.
Land #3510, grammar fix for module descriptions
lands 3469, fixes handler deadlock in corner cases

May affect the following RM issues which need to be retested:
  https://dev.metasploit.com/redmine/issues/8407
  https://dev.metasploit.com/redmine/issues/4314
  https://dev.metasploit.com/redmine/issues/6829