metadata: Implement relaxation of short RBML lengths.

We try to move the data when the length can be encoded in
the much smaller number of bytes. This interferes with indices and
type abbreviations however, so this commit introduces a public
interface to get and mark a "stable" (i.e. not affected by
relaxation) position of the current pointer.

The relaxation logic only moves a small data, currently at most
256 bytes, as moving the data can be costly. There might be
further opportunities to allow more relaxation by moving fields
around, which I didn't seriously try.

0 files changed, 0 insertions, 0 deletions