Merge r1429561 from trunk:

According top my testing 'socache_mc_id2key' is 6x faster with the use 'ap_bin2hex' instead of
apr_snprintf(..., "%02X" for each character.
Output is *not* exactly the same. It was uppercase, now it is lowercase.

According to my understanding, this is not an issue.
Should it be, a call to ap_str_toupper should be added.

The speedup would be less, but still significant.
Submitted by: jailletc36
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1455220 13f79535-47bb-0310-9956-ffa450edef68