sim900: Enable serial receiver

The read option must be set to 'on' in order for two-way
communication with SIM900 module to work.
AUTHORS: Mention Jesper's contributions
sim900: Fix order of dlc prefixes

The order of the defines for the dlc prefixes does not match
the order of the array containing the strings to print.
build-sys: Use libgdbus-internal.la

With the current approach if we have different CFLAGS for each binary we would
build gdbus several times for no reason.

Instead of prepending $(gdbus_sources) to several _SOURCES variable, use
a convenience library thas is used internally only, thus with a "-internal"
suffix.
build: Build a simpler version of libgdbus-internal
atmodem: Add vendor entry for SIM900 module
atmodem: Add gprs-context quirk for SIM900

The SIM900 module from SIMCOM does have a AT+CGDATA command.
However, it is not possible to make a ppp connection when CGDATA
has been used to bring up the gprs context.

This patch adds a quirk that uses the alternative ATD*99***<cid>#
command instead.
sim900: Use SIM900 quirk for gprs context

Use the module specific quirk for gprs by using the vendor entry
OFONO_VENDOR_SIMCOM_SIM900
build: Use dummy=yes assignment for pkg-config check
SIMCOM: add a quirk for AT+CNMI command building

Use mode=1 otherwise it fails (ref. "SIM5215_SIM5216_ATC_V1.18.pdf - §6.9")
SIMCOM: add a quirk for signal strength reporting

We must tell we want the signal strength reporting using
AT+AUTOCSQ command (ref. "SIM5215_SIM5216_ATC_V1.18.pdf - §10.7").
SIMCOM: add a quirk to fix crsm request
atmodem: Fix whitespace violation
handsfree-audio: Make sure to reset has_wideband

When Agent is unregistered we do not know whether the wideband speech is
supported.  Default to false.
bluetooth: Add define for SCO voice settings

Add defines for SCO voice setting (Air Coding). Air mode "Transparent
Data" shall be supported if wide band speech is supported.
handsfree-audio: Initial DBUS code

This code can register an handsfree audio agent and receive NewConnection and
Release calls.
handsfree-audio: Build handsfree-audio command line tool
handsfree-audio: Update .gitignore
handsfree-audio: Add Alsa dependancy
handsfree-audio: Link tool with Alsa