Updated changelog of 6.0 branch

6 jobs for master
Status Job ID Name Coverage
  Test
passed #3153
Linux
clang-c++11

00:22:29

passed #3155
Linux
clang-c++98

00:17:49

passed #3152
Linux
gcc-c++11

00:04:30

passed #3154
Linux
gcc-c++98

00:05:01

passed #3156
Apple
macos-c++11

00:14:39

passed #3157
Apple
macos-c++98

00:09:05