Long-term, once the TX buffering is fixed, this will not be a problem.
In the meantime, it still needs to work. This re-hack fixes the hack.

I have been convinced by rubini and the linux kernel sources.
Opaque types for pointers to struct just make code confusing.

add blocking interface via magical "eb_block" callback
  => causes close to block until complete and return status
  make blocking the default for C++ API
add format pretty-printer helper functions:
  eb_width_data, eb_width_address, eb_format_data, eb_format_endian
add matching parser functions:
  eb_width_parse_address, eb_width_parse_data
use long for delays (int is too short on some platforms)
remove eb_device_flush
  => for now hack around lack of write flow control
add convenience methods eb_device_{read,write}

On falling edge of RX cycle line, push a request to the tag FIFO to lower TX.
Lower the WB master cycle line as soon as no inflight operations.

... split wbm fifo from master outputs
... also named most 32 bit vectors