Fix calling reload twice for package constants and improve hash calculation

[Noremos]

Fixes for the issue described in https://groups.google.com/g/firebird-devel/c/xIxhL_QAjEg : wierd error message when using a consatnt.

To reproduce:

set term ^;
CREATE PACKAGE TEST
AS
BEGIN
    CONSTANT C1 INTEGER = 10;
END^

CREATE PROCEDURE P1(I INT) RETURNS (PROCEDURE_OUTPUT INT)
AS
BEGIN
    PROCEDURE_OUTPUT = TEST.C1;
    SUSPEND;
END^

set term ;^
commit;

select TEST.C1 from rdb$database ;
select * from P1(0);
commit;

[aafemt]

Size of dsc is 12, offset of dsc_address is 8. 12 - 8 = 4. Are you sure that this is a right value?
Perhaps either offset(dsc_offset) or offset(dsc_flags) + sizeof(dsc_flags) should be here.

[AlexPeshkoff]

DSC_SIZE_TO_HASH = offsetof(dsc, dsc_address);