Fix #64937: Firebird PDO preprocessing sql

Fix #64937: Firebird PDO preprocessing sql

This patch fixes some problems with preprocessing SQL queries.

* The new algorithm takes into account single-line and multi-line
  comments and ignores the ":" and "?" Parameter markers in them.

* The algorithm allows the EXECUTE BLOCK statement to be processed
  correctly. For this statement, it is necessary to search for
  parameter markers between EXECUTE BLOCK and AS, the rest should be
  left as is.

The SQL preprocessing code has been ported from Firebird to handle
EXECUTE STATEMENT.

Closes GH-4920.