SYBASE: Added offset support
Fixes: #5294
### Description
Fix for https://github.com/sqlalchemy/sqlalchemy/issues/5294#issue-
610311455
I tested it against our database (Adaptive Server Enterprise/16.0 SP02) with `pyodbc+sybase`
### Checklist
This pull request is:
- [x] A short code fix for #5294
- [x] Added tests.
Closes: #5312
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5312
Pull-request-sha:
f62c14825f2941fdd54ede17fd8d4f105a052e05
Change-Id: Ic716e17a6f654deef78781cefc3f16333cd725c3