Fix our os-stuff after the Rapsody commit:

- add prototype for the new ap_os_dso_init function (gcc complained)
- fix a parse error: the #elif has to use defined(...) (gcc complained)
- fix argument of ap_os_dso_init function (ANSI likes "void")


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82050 13f79535-47bb-0310-9956-ffa450edef68