gr-kernel module and libv4l2_x block

Initial commit.
Generated using gr_modtool.

Signed-off-by: Antti Palosaari <crope@iki.fi>
cmake: add FindV4L2.cmake

Taken from the qx11grab-0.4.7 package.

Copyright 2012 Juergen Heinemann (Undefined) http://www.hjcms.de
Distributed under the OSI-approved BSD License (the "License")

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: initial real implementation

Read /dev/video0 via libv4l2 and output it as a GNU Radio source
complex.

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: implement select file dialog

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: implement set frequency

call VIDIOC_S_FREQUENCY ioctl via v4l2 lib

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: implement set sample rate

Abuses Kernel V4L2_CID_RDS_TX_DEVIATION control currently.

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: use user-class and ext_controls

Define user-class CID_SAMPLE_RATE and not abuse
V4L2_CID_RDS_TX_DEVIATION anymore.

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: implement set bandwidth

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: implement set tuner gain

Currently consider it as a overall tuner gain. Maybe more specific
gain controls are needed...

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: update control IDs according to Mirics Kernel driver

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: use mmap and stream conversion by libv4l2

1) Use v4l2_mmap.
2) Use libv4lconvert for sample conversion.

That implementation is heavily copied from v4l2grab application:
v4l2grab.c (C) 2009 Mauro Carvalho Chehab

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: coding style changes

Use tabs instead of spaces.

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: convert to SDR API

Initial conversion to Kernel SDR API. We do not use libv4l2 format
conversions anymore. Lets add later if needed.

Signed-off-by: Antti Palosaari <crope@iki.fi>
libv4l2: use 1 Hz resolution for RF tuner

Both Kernel SDR drivers are now using 1 Hz resolution.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Merge github.com:palosaari/gr-kernel