Improvement CORE-4590 - Change type of returning value of CHAR_LENGTH, BIT_LENGTH and OCTET_LENGTH of BLOBs to bigint.

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@60172 65644016-39b1-43b1-bf79-96bc8fe82c15