The GL queries are needed only if the user-provided pixel storage
doesn't contain enough information, in particular dimensions and byte
size of compression block.
So in case they are present, no query for compressed image size is done
for full image queries (just saving one API call) and no queries for
block dimensions and byte size for subimage queries (saving four API
calls and not requiring ARB_internalformat_query2).
The documentation was fixed and tests were updated to take the
ARB_internalformat_query2 requirement into account.
Vladimír Vondruš