and adjust the basic test-case, which is surely wrong

The syntax for REPLACE is:

// Replace(expression, find, replace[, start[, count[, compare]]])

surely in the case of a start of 3 the preceeding chars should
be returned unchanged in the result, not stripped off as before
this change.

This reverts commit 869402a5.

Change-Id: Ie710e4de9e7e35c84abe2770142a963532820af4