Merge branch 'MINGW_changes' into 'master'

Mingw changes

TODO: Test 

See merge request !68
7 jobs for OpenMesh-6.1 in 68 minutes and 42 seconds
latest
Status Job ID Name Coverage
  Test
passed #5940
Linux
clang-c++11

00:18:18

passed #5942
Linux
clang-c++98

00:17:20

passed #5945
Linux
cppcheck

00:00:25

passed #5939
Linux
gcc-c++11

00:04:58

passed #5941
Linux
gcc-c++98

00:03:59

passed #5943
Apple
macos-c++11

00:09:05

passed #5944
Apple
macos-c++98

00:14:33