Added support for SET TERMINATOR instruction

[Cybso]

This allows to temporarily change the statement separator with an inline comment and thus supports to execute statements that uses the semicolon within their expression, for example triggers or procedures with BEGIN..END blocks.

Example:

DROP PROCEDURE foobar;

CREATE PROCEDURE foobar
BEGIN
    --#SET TERMINATOR !
    declare v char(10);
    select value into v from sometable;
    if v = 'test' then
        update sometable set value = '';
    end if;
    --#SET TERMINATOR ;
END;

LABEL ON PROCEDURE foobar IS 'Example';

This commit fixes feature request 433 on sourceforge (https://sourceforge.net/p/squirrel-sql/feature-requests/433/).

It currently only supports the default QueryTokenizer. The statement separator is only changed for the current execution.

[gerdwagner]

Was merged with several adjustments. Please take a look if it still works for you. Most of your code is now in the new ChangeStatementSeparatorSupport class.

Thanks for your pull request.

[Cybso]

Was merged with several adjustments. Please take a look if it still works for you. Most of your code is now in the new ChangeStatementSeparatorSupport class.

I haven't completely figured out the integration, but it looks pretty good at first glance. I have added three small notes to the commit. In particular, the method isCommandPrecededBySpacesOrTabsOnly is named incorrectly or the return value is the wrong way around. However, since the call also takes this into account, it still works at the moment, it's just not intuitive:

      if(isCommandPrecededBySpacesOrTabsOnly(_script, searchStartPos))
      {
         return null;
      }