Revert "CPPFLAGS -> CFLAGS in Makefile.am"

This reverts commit e2f5660db827e9801f5c4d1fd9d16088a23578fc.

Conflicts:
	Makefile.am
build: move -fstack-protector to Makefile.am

Setting -fstack-protector in AM_CFLAGS is better than setting it
in configure with CFLAGS="-fstack-protector $CFLAGS"

There is also a big cleanup in Makefile.am in this change.
build: fix warnings exposed by fixing radvd_CFLAGS

There were a few minor problems that crept in after radvd_CFLAGS was
broken.  There was also, at least, one major bug where setup_iface was
taking the iface where it was expecting sock.
scanner.l: prototype get and set column

Using a reentrant scanner causes flex to used some unprototyped
functions.  I considered simply removing the -Wmissing-prototypes.
But after discovering setup_iface was being passed the wrong
parameters when another bug was preventing that compiler switch
from being passed to radvd, I decided that those warning are
essential.

This change simply adds prototypes the two missing function
prototypes.
build: modernizing configure

I kept getting a warning that two and three arg versions of
AM_INIT_AUTOMAKE was deprecated and I should fix the problem using
instructions found here...

http://www.gnu.org/software/automake/manual/automake.html#Modernize-AM_005fINIT_005fAUTOMAKE-invocation

...I attempted to fix this a few times, but this change envolved
setting VERSION explicitly in configure.ac, not in the VERSION
file.  I found that I could accomplish the same thing with AC_INIT
while ditching the VERSION file at the same time.  The idea is
instead of the VERSION moving like so...

VERSION >> confugure

...we can do this...

configure >> VERSION