Fix warning "dereferencing type-punned pointer will break strict-aliasing rules".
Fix m32_tx_acquire not checking the HOLD bit properly.
Fix warning "suggest parentheses around operand of ‘!’ or change ‘&’ to ‘&&’ or ‘!’ to ‘~’".

Note: the datasheet isn't available anymore, so the intended behavior was inferred from surrounding code; it was assumed that the hold bit is managed elsewhere
Fix warnings "assignment discards ‘const’ qualifier from pointer target type" by copying the backplane/supervisor eeproms.
Fix memory leaks of c6sup1_t.slot_eeprom data.