Added support for SET TERMINATOR instruction

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:

```sql
DROP PROCEDURE foobar;

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

--#SET TERMINATOR ;
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.

Author: Cybso

sql12/core/src/net/sourceforge/squirrel_sql/fw/sql/querytokenizer/QueryTokenizer.java

@@ -164,6 +164,22 @@ public void setScriptToTokenize(String script)
         for (int i = 0; i < script.length(); ++i)
         {
            final NextPositionAction nextPositionAction = commentAndLiteralHandler.nextPosition(i);
+           if (!commentAndLiteralHandler.isInLiteral() && !commentAndLiteralHandler.isInMultiLineComment()) {
+               // Check for a line that contains '--#SET TERMINATOR x' to change the current new statement separator
+               if (script.startsWith(_lineCommentBegin + "#SET TERMINATOR ", i)) {
+                   if (i == 0 || script.charAt(i-1) == '\n') {
+                       // Only when the comment starts on a new line
+                       int newLinePos = script.indexOf('\n', i);
+                       if (newLinePos > 0 && newLinePos > i+18) {
+                           String terminator = script.substring(i + 16 + _lineCommentBegin.length(), newLinePos).trim();
+                           if (!terminator.isEmpty()) {
+                               s_log.info("changing statement separator to '" + terminator + "'");
+                               setQuerySep(terminator);
+                           }
+                       }
+                   }
+               }
+           }
 
            curOriginalQuery.append(script.charAt(i));