2016-08-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    * doc/fragments.texi (MULTILIB_REUSE): Mention that only options in
    MULTILIB_OPTIONS should be used.  Small wording fixes.
    * genmultilib: Memorize set of all option combinations in
    combination_space.  Detect if RHS of MULTILIB_REUSE uses an option not
    found in MULTILIB_OPTIONS by checking if option set is listed in
    combination_space.  Output new and existing error message to stderr.

From-SVN: r239734