Add file mapping to phpstan

[EdwinHuijsing]

This should solve issue #4372 "phpstan filename mappings not respected when running via docker".

Vim 8 caused a problem in one test, because the error vim returns is not the same as the other three.

[EdwinHuijsing]

I just rerun the docker test ./run-tests -q and no problems where reported.
"continuous-integration/appveyor/pr" runs on windows, looks like there is the cause of the test problem.
Will the patch work on windows? If the mapping is filled correct, i see no reason why it would give an problem

Any ideas who to fixes this? I can't test on windows (i don't have windows), so i am out of options.
I need a way to give the buffer a fixed full path, i have search before but i can't find way to give the buffer a fixed full path.

Regards,
Edwin

[EdwinHuijsing]

Yesterday while working on an other linter, i found that we do not need the filename.
So i need to review the changes i did, locally i now have an version running that only
added two lines and changes one line.

More testing is needed before i can push the changes

Regards,
Edwin

[hsanson]

LGTM.