build: explicitally request for SED to be defined and propagated
build: explicitally request for SED to be defined and propagated

autoconf 2.60 and higher set and replace the SED program, so use
corresponding macro explicitally for using it or a simple SUBST
for cases where older versions of autoconf were used to bootstrap.


git-svn-id: 27e0aca8c7a52a9ae65dfba2e16879604119af8c@2291 93a4e39c-3214-0410-bb16-828d8e3bcd0f

fastly/ganglia,fastly/ganglia,fastly/ganglia,fastly/ganglia,fastly/ganglia