Merge branch 'iter-fixes' into 'master'

Fix operator-- in some of the new iterators

See merge request !69
9 jobs for master in 6 minutes and 29 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #78250
VS2015
VS2015-32-bit

00:01:18

passed #78249
VS2015
VS2015-64-bit

00:01:27

passed #78248
VS2017
VS2017-32-bit

00:01:18

passed #78247
VS2015
VS2017-64-bit

00:01:43

passed #78244
Linux
clang-c++11

00:04:11

passed #78246
Linux
cppcheck

00:06:28

passed #78251
Linux
doc

00:00:36

passed #78243
Linux
gcc-c++11

00:04:08

passed #78245
Apple
macos-c++11

00:01:49