Update Subversion to 1.14.0 LTS. See contrib/subversion/CHANGES for a
summary of changes, or for a more thorough overview:
https://subversion.apache.org/docs/release-notes/1.14
NOTE: there is no need to dump and reload repositories, and the working
copy format is still the same as Subversion 1.8 through 1.13.
Relnotes: yes
MFC after: 2 weeks
X-MFC-With: r361677