scripts

I have no idea why, but the installed "sed" wrapper never terminates
on RHEL.  If I don't use the wrappen the the tools build fine, so this
just uses the already set autoconf variables to attempt to determine
if the system sed/awk are gsed/gawk and if they are then this avoids
using the wrappers.

There's a few oddities here:

* I have no idea why the sed wrapper fails, as it seems super safe.

* I haven't run into any awk problems, but I figured I'd treat it the
  same as it isn't any harder.

* We shouldn't have to support 10 year old distributions.

Hopefully this doesn't break anyone's builds...