Clean up Linux configuration by detecting 2.x linux and enabling HAVE_SHMGET,

and HAVE_SYS_RESOURCE_H.  Don't touch Linux 1.x systems for fear of various
compatibility problems.  Ditch that silly hack LINUX_TWEAK that I wish
I hadn't introduced.

Reviewed by:	Paul S., Roy


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@78037 13f79535-47bb-0310-9956-ffa450edef68