Here is the reason for the old version of pcre:
# DirectAdmin added pcre 8.21 to custombuild in december last year, however it was having a bug that created problem for people running vBulletin
http://www.directadmin.com/forum/showthread.php?t=42532 - because of that, DirectAdmin downgraded pcre 8.21 to pcre 8.20 in custombuild.
# When pcre 8.30 was released, the vBulletin bug was fixed in that version, and DirectAdmin upgraded pcre in custombuild from version 8.20 to new version 8.30. But the new version pcre 8.30 did have problems with new DirectAdmin installs (existing installs did not get problems), because of that, DirectAdmin downgraded only a few minutes later from pcre 8.30 to pcre 8.20 in custombuild. Here is John replys about this on email dated March 7, 2012:
I actually had to downgrade pcre again.
Existing installs are fine to use pcre 8.30 (exim won't even use it without a recompile), but for new installs, all exim binaries are still linked against the old libpcre.so.0, whereas the new version creates libpcre.so.1, this will break exim since libpcre.so.0 won't exist.
I'll have to:
1) have custombuild create links to the new version from the old link
2) test to ensure that the existing binaries, which are build vs the old version, still work with the new one... as there may be linking mismatches.
So to summarize, pcre 8.21 has bug causing trouble for vBulletin, that bug was fixed in pcre 8.30, but pcre 8.30 cause problems as John describe in quoted text above.
I have now sent DirectAdmin support email and asked him to try to find a solution to all this, so that he can add the new released pcre 8.31 to custombuild.
Edit: I found this about pcre 8.30
http://www.directadmin.com/forum/showthread.php?t=43043 - please see user "Arieh" reply to that thread, he say httpd wouldn't compile after upgrade to pcre 8.30. I would guess that should be related to the problems John explain in the quoted text above, but I don't know.