Log Message:
By using ENABLE_GR_xxx cmake variable, split gnuradio into small
modules.  Aside from that, gnuradio-default is prepared to build with
upstream default(ENABLE_DEFAULT=True).  This -default is for the
refererence to see if meta-pkgs/gnuradio covers with its -default version

There are PLIST overwraps if just using ENABLE_GR_xxx variables.
One between all the modules and gnuradio-core. The others are between
gnuradio-atsc and gnuradio-fec, and between -trellis and -digital.
Those combination sound natural, because former depends the latter
(But latter alone can be packaged).

The work around of above problem is that
having removing-overwrapped-PLIST-script in post-install: target.
(on Nocore.mk)

Common stuff, Makefile.version, Makefile.common, distinfo, patches
are moved from meta-pkgs to gnuradio-core. I believe it is natural location.

To check the consistency over various PLIST's, perl script 
check-PLIST-overwrap is at gnuradio-core/files. This is only for
PKG_DEVELOPERS. Have -h for usage.  Overwaps and Missing (from
gnuradio-default) of PLIST's will be shown by this.

(Other files will be committed later)