add support for iio which is used by the PLUTO.

bootstrap.sh

@@ -1,7 +1,7 @@
 apt-get update
 apt-get install -y xauth
 apt-get install -y gnuradio
-apt-get install -y gr-osmosdr
+apt-get install -y gr-osmosdr gr-iio libiio-utils
 
 # audio
 #apt-get install -y linux-sound-base alsa-utils