Allow for special fallback rom slot#16

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ToSa27 wants to merge 5 commits intoraburton:masterfrom

ToSa27:master

Commits on May 27, 2016

Commits on May 29, 2016

Treat rom slot 0 as special fallback rom. Enable by setting new flag MODE_FALLBACK in mode byte.
ToSa27
committed

Commits on Jun 19, 2016