build: Add automatic compare of config.h files to recursive waf build

build: Add automatic compare of config.h files to recursive waf build

This uses the fact that we have both build systems running at the same time.

The krb5 checks are skipped because we typically are comparing internal Heimdal
with the system krb5, so they do not make sense.

The required checks for krb5 are pretty well understood in any case, as
we have a limited set of supported libraries.

Andrew Bartlett