MFH: r552897

misc/iio-oscilloscope: fix build on GCC architectures

Use C11 compiler:
cc1: warnings being treated as errors
In file included from /usr/local/include/glib-2.0/glib/gthread.h:34,

from /usr/local/include/glib-2.0/glib/gasyncqueue.h:32,
from /usr/local/include/glib-2.0/glib.h:32,
from /usr/local/include/glib-2.0/gmodule.h:28,
from /wrkdirs/usr/ports/misc/iio-oscilloscope/work/iio-oscilloscope-0.11-master/iio_utils.h:11,
from /wrkdirs/usr/ports/misc/iio-oscilloscope/work/iio-oscilloscope-0.11-master/iio_utils.c:1:

/usr/local/include/glib-2.0/glib/gutils.h:336: warning: 'GVoidFunc' is deprecated

Also remove previous patches that fixed build with base GCC of previous version of the port.

Approved by: portmgr (fix build blanket)