cpimport would truncate UTF8 data half way through a character which
would cause problems for functions using that data. This patch
calculates the correct truncation point when inserting the data.
The signatures were getting destroyed whilst processing before being
used in the dictionary de-duplication cache making the cache full of
empty strings. This fix resets the signature after insertion for the
cache.
This fix also lets the signature cache be read when there is 1000
entries in it.
* DML writes for multi-block dictionary (blob) now works
* PrimProc fixed so that the first block in multi-block is read
correctly
* Performance optimisation (removed string copy into stack) for new
dictionary entries
