Merge r741862, r741866 from trunk:

Add object perms set macros and implement them for shm and mutex
Submitted by: mturk, rpluem
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/branches/1.6.x@1590617 13f79535-47bb-0310-9956-ffa450edef68