Improved Hibernate ORM Firebird dialect support

Mark Rotteveel created a Ticket and Pull Request for Hibernate ORM to improve Firebird dialect with fixes to a number of issues.

Improve Firebird dialect to fix a number of issues:

• Typing of aggregates when using parameters
• Add cast to AVG of integral type
• Quote identifiers starting with an underscore
• Correct inverted version check for Boolean support
• Add or update various supports methods to return correct information
• Render datetime literals without using JDBC escape
• Fix rendering of literals with offset at offset 00:00
• Fix rendering of create index statement
• Fix rendering of CASE where all when clauses have a parameter to identify type of result
• Add missing rendering of virtual columns to select list
• Fix rendering of IN against a parameter

Updated a number of tests so they are either passing for Firebird, or ignored for Firebird.