fhs.c: Correct permissions for /var/mail and /tmp

fhs.c: Correct permissions for /var/mail and /tmp

- /var/mail is looking for 0755 but dma is setting 02775
   checking FHS it looks like the settings should be 02775
- /tmp is being checked for 1755 instead of 01755 so the number is
   not being recognised as octal but as decimal
- The /var/mail change confirmed to allow dma to be built in ipfire3.x
   without failing for FHS errors

Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>