mod_graylog2: channel variables can now be automatically added as gelf additional fields in logs w/ session UUID

`curl_sendfile` generates a multipart message with Content-Type:
multipart/form-data with no separate Content-Type headers in the parts
for each non-file argument.  These parts therefore default to
text/plain.  However, prior to this commit, we were putting the URL
encoded POST data into these parts, which is not correct.  We should
be putting raw text into the parts.

With this commit, we urldecode each argument key and value before
composing the multipart message.

See:

  http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.2

* commit 'd1abf274':
  REFER_EVENT is missing from the message names array

* commit '4d0b875d':
  fix mod_fifo presence https://jira.freeswitch.org/browse/FS-6732

usleep is deprecated and disabled in glibc 2.12 unless requested. Use
nanosleep instead if available.

This fixes the following compiler warning:

    ./src/zrtp_iface_scheduler.c: In function 'zrtp_sleep':
    ./src/zrtp_iface_scheduler.c:96:2: warning: implicit declaration of
    function 'usleep' [-Wimplicit-function-declaration]
      usleep(msec*1000);
      ^

These two files should only be built when OpenSSL is not enabled. See
the configure script of the original sources and Makefile from upstream.
(RNG_EXTRA_OBJS)

Fixes a -Wimplicit-function-declaration warning.

* commit '05ef1894':
  add uptime api to mod_commands

* commit 'b60df39b':
  mod_http_cache: fix configuration so that carriage returns or other whitespace is OK around S3 keys
  mod_http_cache: fixed S3 URL parser to allow mybucketsubdomain.com.s3.amazonaws.com

https://jira.freeswitch.org/browse/FS-6732

* commit 'fe2a6e8a':
  FS-6620 mod_blacklist fix not deleting entries from list

REFER_EVENT has been added to switch_core_session_message_types_t
a while ago, but was never added to the message_names[] related array.