Purpose
Writes a database header block (a WIDindex entry) into the
given WordInfo. This is split into a separate routine so that
the library can write a word block header tentatively, using a
different format for the header if the header and the data all
fit into the index block.
LQT_MakeWordInfoBlockHeader determines
the format to use by whether WordInfo->Offset is non-zero.
The difference is whether a fixed four bytes are used for the
total number of word places for this word, or whether a variable
number of bytes, using
LQT_sWriteNumber, are written. In the
latter case, update in place is not possible, and this format is
therefore only used when WordInfo->Offset is zero, and any update
would in any case have to read and rewrite the word index block.