Merge r1488492, r1542533, r1543020 from trunk:

Check if malloc succeeded
PR54344 [Bill Parker, wp02855 gmail com]

Check all memory allocations and abort on failure


follow-up to r1542533:

fix format string (unsigned vs. size_t)

Submitted by: jailletc36, sf, trawick
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1554214 13f79535-47bb-0310-9956-ffa450edef68