Add the same conditions for initgroups() existance as we use in apache's conf.h;

Add case insensitivity for BS2000's user name comparison (yes, that's how it is);
Add an error message if the executable isn't executable.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80612 13f79535-47bb-0310-9956-ffa450edef68