Vif_Transfer.c and Vif_Codes.c are the VIFcode interpreter and its
command handlers in C89. Each handler is written once against the unit
index and the table holds a thin per-unit entry for it, the per-unit
state is reached through VIF_X, VIF_XCH and VIF_XREGS, and the C++ is
reached through small C entry points: vif_unpack_setup and vif_unpack
in Vif_Unpack.cpp, mtvu_write_col and mtvu_write_row in MTVU.cpp,
gif_unit_transfer_direct for DIRECT and DIRECTHL, and vu1ExecMicro and
vifCmdHandler now with C linkage.
tests/eevifcode feeds both units seeded VIFcode streams, every command
and unknown codes included, in random chunks and as tags, and checks
the result against the previous C++.
