bluetooth: Minor style fixes

Fix some minor style fixes to be consistent with the project coding
style.
bluetooth: Consider different input and output MTU

Previous implementation assumes these values are equal, but this doesn't
necessarily have to be so.
bluetooth: Avoid duplicating profile argument twice

The module module-bluetooth-device should never be given parameter
'profile' twice, even if both HFGW and A2DP are playing. This patch
proposed to consider HFGW first.
bluetooth: Replace deprecated ListAdapters()

The method ListAdapters() in org.bluez.Manager was deprecated in BlueZ
4.61, and is going to be removed in future releases. Instead, a property
was introduced for this purpose in BlueZ 4.22.
bluetooth: Replace deprecated ListDevices()

The method ListDevices() in org.bluez.Adapter was deprecated in BlueZ
4.61, and is going to be removed in future releases. Instead, a property
was introduced for this purpose in BlueZ 4.7.
bluetooth: Remove minor unnecessary check

The return value of dbus_message_iter_next() doesn't need to be checked
since the while condition will be false anyway (arg type will be
DBUS_TYPE_INVALID).
modules: Add null/dummy echo canceller

I find a dummy/passthrough implementation useful for AEC debugging

Signed-off-by: Peter Meerwald <p.meerwald@bct-electronic.com>
build-sys: add `check` test framework
tests: modify mix-test to use new 'check' test framework
tests: add cpu test

It tests only x86 architecture right now.
tests: modify mainloop-test to use new 'check' framework
tests: modify utf8-test to use new 'check' test framework
tests: modify strlist-test to use new 'check' framework
tests: Factor out Orc test code into cpu-test

Reorganises all the svolume core test code in cpu-test since it's the
same across MMX/SSE/etc.
tests: Make cpu-test less verbose
build: add a target to ease the creation of coverage files
tests: enable to test standalone pulseaudio daemon

With this fix, `check-daemon` doesn't need a system-wide running pulseaudio
anymore.

The method to use is to invoke `make check-daemon` under `src/` and it just
works! :)
build-sys: webrtc-utils needs to be installed before module-echo-cancel

Like other plugin helper libraries these need to be installed
before the plugins that use them..
build-sys: Link utf8-test to libpulsecommon.

Fixes this:
/usr/bin/ld: utf8_test-utf8-test.o: undefined reference to symbol 'pa_log_set_level'
/usr/bin/ld: note: 'pa_log_set_level' is defined in DSO /home/takaskin/dev/pulseaudio/src/.libs/libpulsecommon-2.98.so so try adding it to the linker command line
/home/takaskin/dev/pulseaudio/src/.libs/libpulsecommon-2.98.so: could not read symbols: Invalid operation
resampler: Fix volume on downmix to mono

Patch credit: kwanghui

When downmixing to mono, we should average the signal instead of
summing it to avoid clipping.

BugLink: http://pulseaudio.org/ticket/934
BugLink: https://bugs.launchpad.net/bugs/416190

Signed-off-by: David Henningsson <david.henningsson@canonical.com>