pseudomodem: Added SMS support.

Pseudomodem can now simulate fake SMS reception. It doesn't yet handler
multi-part SMS.

BUG=chromium:268573
TEST=1. stop modemmanager; stop cromo; pseudomodem -f 3GPP -i
     2. In the shell run 'sms 15555555555 This is a fake SMS message.'
        The UI should notify the arrival of a new SMS.

Change-Id: Iceadfd77cf0bd436c6f1b781311de37d28d61395
Reviewed-on: https://gerrit.chromium.org/gerrit/65037
Commit-Queue: Arman Uguray <armansito@chromium.org>
Reviewed-by: Arman Uguray <armansito@chromium.org>
Tested-by: Arman Uguray <armansito@chromium.org>
7 files changed