Fix recognition of variant 11x17+16_shogi

Fix recognition of variant 11x17+16_shogi

The general recognition of size-overridden variants prevented that an
name with override prefix was still sought as a full name. And because the
17 does not correspond to the true number of ranks, 11x17+16_shogi was not
recognized from the board parameters either.
  The duplicate of euroshogi as size-overridden shogi was misguided, and has
been removed: description of a variant by size overrides is now always
recogized automatically.