Move initgroupgs, ap_uname2id and ap_gname2id from util.c to

mpm_common.c.  These functions are only valid on some platforms,
so they should not be in the main-line code.

These functions are also not portable to non-unix platforms, so they don't
really belong in APR.  Since they are only used in MPMs, for right now,
I am moving them to mpm_common.c


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87755 13f79535-47bb-0310-9956-ffa450edef68