Write a reference to the data ptr[0..size+nzeros]
Append dt to data.
Append dtb to data.
Write reference to offset in code segment.
Create a reference to another dt.
Write 4 bytes of value.
Finish and return completed data structure.
Return true if size of data is 0.
Return size of data.
Append data represented by ptr[0..size]
Write a bunch of zeros
Repeat a list of dt_t's count times.
Write a size_t value.
Write a reference to s+offset
Create reference to s+offset
Like xoff(), but returns handle with which to patch 'offset' value.