bug#8784: Support developer-reserved AM_DISTCHECK_CONFIGURE_FLAGS

[Stefano Lattarini]

Severity: wishlist

Hello automakers.

Continuing with the good trend of avoiding to impinge on the user
namespace, we should start supporting AM_DISTCHECK_CONFIGURE_FLAGS
in addition to DISTCHECK_CONFIGURE_FLAGS, so that the former can be
reserved for the developer to be set in the 'Makefile.am's, and the
latter left for the user, packager or tester to use freely.

Sorry for the curtness of this message, but it is thought more as
a "note to self" than a bug report proper.

Regards,
  Stefano