Make some *PropertyT constructors private to prevent accidental misuse.

These constructors were introduced in 26e2fe64 to implement clone(),
but their signature might suggest uses that would result in memory corruption.
11 jobs for private-cloning-constructors in 4 minutes and 2 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #52573
VS2013
VS2013-32-bit

00:00:56

passed #52572
VS2013
VS2013-64-bit

00:00:56

passed #52571
VS2015
VS2015-32-bit

00:01:22

passed #52570
VS2015
VS2015-64-bit

00:01:07

passed #52569
VS2017
VS2017-32-bit

00:01:24

passed #52568
VS2015
VS2017-64-bit

00:01:15

passed #52565
Linux
clang-c++11

00:03:43

passed #52567
Linux
cppcheck

00:00:47

passed #52574
Linux
doc

00:00:21

passed #52564
Linux
gcc-c++11

00:04:01

passed #52566
Apple
macos-c++11

00:01:35