Added an option to start the search for the first complete expression
from more than 1 line behind the original source location.

This allows source extraction from procs like this

    my_method "hi", {
      :a => 1,
      :b => 2
    } {
      <proc body>
    }

previously the search would star from "} {" and immediately raise a
SyntaxError.  In this version, the search keeps backing up 1 line
at a time (up to some max number of lines, 5 by default), until
it find the beginning of the expression.