WL#3397 Refactoring storage engine test cases (for falcon)
    It contains also fixes according to code review.
    Contents: Testcases which were in history dedicated to InnoDB or MyISAM only.
    Modifications:
    1. Shift the main testing code into include/<testing field>.inc
       Introduce $variables which can be used to omit tests for features which are not supported by
       certain storage engines.
    2. The storage engine to be tested is assigned within the toplevel script (t/<whatever>_<engine>.test)
       via variable $engine_type and the the main testing code is sourced from 
       include/<testing field>.inc
    3. Some toplevel testscripts have to be renamed to
       - avoid immediate or future namespace clashes
       - show via filename which storage engine is tested
    4. Minor code cleanup like remove trailing spaces, some additional comments ....