Fix CouchJS compatibility with older Spidermonkey.
Fix CouchJS compatibility with older Spidermonkey.

The recent patch to enable support for SM 1.8.5 broke support for
1.7.0. This patch updates couchjs to work with all of the major
variants of Spidermonkey.

Versions tested:

    1.7.0
    1.8.0rc1
    1.8.5
    1.9.2.something (XULRunner)

Various combinations have been tested on OS X, Ubuntu, FreeBSD and
Windows.

Fixes COUCHDB-1260



git-svn-id: c1f8a8ec0b3bb2e99ab3413722f81f687760e79c@1164346 13f79535-47bb-0310-9956-ffa450edef68

apache/couchdb-futon,apache/couchdb-futon