Add git version to make VERSTR

Add git version descriptor to the VERSTR
make variable.
Rename variable to clarify code

Rename the variable 'rx' to 'regxp' to prevent
masking of a member variable of same name.

Show the name of the device if regexp not match
instead of 'Unknown'.  Rtlsdr device shows as
"rtl=0".
Revert "Add git version to make VERSTR"

It is intentional that we display version 0.0 when people build
from git in release mode.
This reverts commit 4bb00b39042c271bfedafdbd23b6a02e846ee6cc.
Rename regxp to regexp.
We always require gnuradio-core.
Set lower limit on AM and FM filter width to 500 kHz. Prevents application freeze.
Try to organize include files alphabetically.
Introduce some input/output pasrameter checks.

When setting device strings or sample rate, check if the new settings
asre different from the old ones and do nothing if the settings haven't
changed. The reduces the number of 'i/o device errors' since we don't
try to re-open the same device.
Suspend DSP during reconfiguration.
Enable automatic tuner gain by default.
Update suggested sample rates for rtlsdr devices.
Updated.
Updated news file.
Merge pull request #1 from csete/master

merging fork