NTFS/FAT: don't use umask=000 but dmask=000,fmask=111 instead

NTFS/FAT: don't use umask=000 but dmask=000,fmask=111 instead

Leave directories as they are, but don't provide files with file
permissions 777 AKA executables, but in mode 666 instead. This
still provides writeable files but they aren't recognized as
executables (e.g. by file managers).