Apply the LCONVPATH() to the (old) linux_stat() and linux_lstat() syscalls.
Without it, code has two problems:

• behaviour of the old and new [l]stat are different with regard of the /compat/linux
• directly accessing the userspace data from the kernel asks for the panics.

Reported and tested by: Peter Holm
Reviewed by: rdivacky
MFC after: 3 days