Bering does not ignore SQL line comments in external()

[rsutphin]

Issue copied from google code.

What steps will reproduce the problem?

1. Set up a migration that contains a line comment that includes a semicolon
2. Execute the migration

What is the expected output? What do you see instead?

Expected: the line comment is executed.
Actual: bering attempts to execute just the comment. With some databases, this provokes a JDBC error. (Seen on Oracle, but may apply to others.)