Ignore new compiler warnings in gcc 8.2.0

I was testing the new Debian "buster" image by @RobertCNelson and we noticed that the Adafruit_BBIO build was failing on compiler warnings.  This seems to be due to the introduction of new compiler warnings in the more recent version of gcc that is on the buster image: https://rcn-ee.net/rootfs/bb.org/testing/2019-03-03/buster-iot/bone-debian-buster-iot-armhf-2019-03-03-4gb.img.xz a shot

Author: pdp7

setup.py

@@ -21,7 +21,7 @@
 else:
     kernel41 = None
 
-CFLAGS = ['-Wall', '-Werror', '-Wextra', '-Wno-missing-field-initializers', '-Wno-strict-aliasing' ]
+CFLAGS = ['-Wall', '-Werror', '-Wextra', '-Wno-missing-field-initializers', '-Wno-strict-aliasing', '-Wno-cast-function-type', '-Wno-error=format-truncation=', '-Wno-error=sizeof-pointer-memaccess' ]
 
 classifiers = ['Development Status :: 3 - Alpha',
                'Operating System :: POSIX :: Linux',