Fix Sybase schema due to obscure syntax errors
An UTF8 character in a comment make Sybase choke with:
TinyTds::Error: Incorrect syntax near '@@@V0_INT91@@@V1_INT91'
Didn't investigate much, as the characters were located in comments
used only to keep the schema files up to date.
Add abstraction for different IDENTITY functions
Disable some tests for ASE, fix some others