For supported versions of Darwin, place dynamically loaded

For supported versions of Darwin, place dynamically loaded
Apache extensions' public symbols into the global symbol
table. This allows dynamically loaded PHP extensions.
NOTE: this works as long as multiple modules don't
include overlapping symbols. Jim added the wrapper to
check for the existance of the option (which doesn't
exist in Rhapsody).

PR:
Obtained from:
Submitted by:	Marko Karppinen <markonen@php.net>
Reviewed by:	Jim Jagielski, Wilfredo Sanchez

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@94753 13f79535-47bb-0310-9956-ffa450edef68