expected behavior of --with-debug

[Jeff Kaufman]

In ngx_pagespeed we interpret --with-debug to mean "include debugging
symbols and debug-only assertions".  Is this what most people using
nginx would expect?

(We distribute two precompiled versions of PSOL, "debug" and
"release", and we've been using --with-debug to switch between them.
Now we're wondering if this is an abuse of that flag, and if we should
instead add our own flag to specify which precompiled version to use.)