Import Apache apr-util-1.5.2 into vendor staging area.
Update subversion-1.8.0 -> 1.8.1.  Update supporting
components: apr-1.4.6 -> 1.4.8 and apr-util-1.4.1 -> 1.5.2.

This is a post point-zero bug-fix / fix-sharp-edges release, including
some workarounds for UTF-8 for people who haven't yet turned on WITH_ICONV.
mdoc and language improvements.
Remove EOL whitespace.