When bridging a call, the to-tag used in the outgoing 180 Ringing
message for the inbound channel is unavailable until the channel has
been answered. For the outgoing channel this value is already available
through the sip_to_tag variable via the event socket.

This is solved this by setting sip_to_tag to the local leg's tag when
receiving a ringing indication for inbound channels. This will also make
the variable available in the CHANNEL_PROGRESS event through event
socket.

FS-7137 #resolve

Setting the 240k hard limit here is too aggressive and causes FS to
crash on startup.

Previously data returned from `memcache get` would be truncated at the
first NULL byte.

By using raw_write_function here to stream the returned memcache
value, we allow mod_memcache to be used for audio and other arbitrary
binary data.

Dave has a format module planned that relies on this.

Thanks-to: Dave Olszewski <dolszewski@marchex.com>

FS-7114 #resolve

ClangFormat is an attempt to build something like gofmt for C.

ref: http://clang.llvm.org/docs/ClangFormat.html
ref: http://clang.llvm.org/docs/ClangFormatStyleOptions.html

The clamp(v,a,b) function wraps v around the interval [a,b).

However prior to this commit, `clamp` was ignoring the third argument
and using the second argument again in its place.  This resulted in a
division by zero.  Hence `clamp` didn't work at all.

Even if the arguments were treated correctly, `clamp` incorrectly
multiplied rather than added whenever v < a.  This would have produced
bogus results.  (Thanks to Shona McNeill for pointing this out.)

Note that as implemented, `clamp` is undefined for b >= a.

These errors are present in the last upstream C version, v2.7.
They've been corrected in the C++ version that upstream now maintains
instead.

Thanks-to: Shona McNeill <prufrax@googlemail.com>

FS-7070 #resolve

With this commit we allow getting `make -jN` behavior by setting
`parallel=N` in `DEB_BUILD_OPTIONS`.  Setting `parallel=` will result
in `make -j` being run (i.e. no limit on the number of jobs).  The
default is to run one job at a time; this is still the safest bet when
building all modules.

Thanks to Peter Wu for suggesting a different way to do this.

ref: https://www.debian.org/doc/debian-policy/ch-source.html#s-debianrules-options

The lsb-release package isn't a stated dependency and isn't present on
a minimal Debian install.

* commit '0822f6a0':
  FS-7019 swap debian/ubuntu autodetection order
  FS-7019 detect debian explicitly, error on unknown distribution
  FS-7019 add note on how to build on Ubuntu
  FS-7019 full list of distributions to target based on distribution autodetection
  FS-7019 build error on utopic (lber_types.h: No such file or directory)
  FS-7019 add support for building on ubuntu trusty and utopic

* commit '83acda04':
  file_string write failover FS-4930

FS-7083 #resolve #comment this should do it.  The problem is linked to side-effects from the read thread being delayed by writing to the file handle.  It was so much worse on mp3 because the shout encoder blocks while its churning the data and delays it more.  This patch adds a dedicated thread for writing to the file and the channel_variable RECORD_USE_THREAD=false will disable it and sync may still be maintained at the cost of dropping more data from the audio signal.

* commit 'c96d64e7':
  invalid type cast correction
  list_users tipo correction