Add "conditional failure" result to configtest.php

[rjl]

In addition to the green (OK) and red (FAILURE) results that configtest.php produces, an orange or yellow "conditional failure" category should be added to indicate items that aren't necessarily fatal errors. For instance, MySQL or PostgreSQL is required, but not both, so the absence of a PostgreSQL library is not necessarily a fatal error, provided that a MySQL library is present. If both are missing, however, the error is fatal.

[dmorton]

er, I guess I already did this while working on refectoring the file. see #2