Make byte_tester to be able to test a block of bytes without defining the tags and the data

[vhelin]

Here's how tests are currently defined:

    .db "01>"               ; @BT TEST-01 01 START
    mul d, e                ; @BT ED 30
    .db "<01"               ; @BT END

Add support for something like this:

  ;@BT TEST-01 01 START2 $1000
  ;@BT 01 02 03 04
  :@BT END

Here START2 (we need a better name for this) starts testing bytes at $1000