sane defaults with [u,d,f]mask for [v]fat

Binary package hint: udisks

Misconfigured options and permissions mapping for fat filesystems can cause quite diverse problems: Bug #118283, Bug #592748, ...

To privide a better configuration, some mount options should be derived from the current umask, rather than be hardcoded options.

Generally, a filesystem can get mounted privately for a single user/group or
shared.

As a default, it should be a sane to mount privately. I.e. this means with permission corresponding to the current user's
umask. (When detecting the umask note that umask might be set differently for
root, and thus for the running script than for the current console user)

Additionally, udisks could provide options to mount with specific permissions. (i.e. --user-only, --user-and-group-only, --public, or --userdefined permissions)

For best VFAT integration not only on multi user systems here are tested mount
options:

On systems that use umask 002 add:
",quiet,shortname=mixed,dmask=0002,fmask=0113" to the vfat mount options.

On systems with umask 022 add:
",quiet,shortname=mixed,dmask=0022,fmask=0133" to the vfat mount options.

Non-english systems benefit using multilingual codebase with
",codepage=850" in the vfat mount options.

If the system uses UTF8 also add
",iocharset=utf8" to the vfat mount options.