Sync'ing FSX with FSFS:
Merge r1547134,1575431,1575436,1580391 from /subversion/libsvn_fs_fs
into subversion/libsvn_fs_x.  Conflicts were due to structural
differences between FSX and FSFS.

This ports addresses a number of cache config edge cases.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1595322 13f79535-47bb-0310-9956-ffa450edef68