Ticket #1642: filegui.c contains Linux-specific things

Ticket #1642: filegui.c contains Linux-specific things

mc 4.7.0-pre1 introduced dynamic "Save attributes" checkbox value in Copy/Move dialog.
But code is Linux-specific, and not even isolated by macros.

I suggest to add code specific for BSD and SVR4 systems.

In BSD systems (MacOS X, NetBSD, FreeBSD) there is statfs.f_fstypename which contains name of filesystem.
Valid FS names are: msdos, msdosfs (FreeBSD), ntfs, smbfs, procfs, fusefs (BSD), fusefs_subfstype (Mac)

In SVR4 systems (Solaris and other SVR4 Unixes) there are statvfs.f_basetype and statvfs
syscall instead of statfs and also autotools define STAT_STATVFS.
Valid FS names are: pcfs, proc, ntfs, fuse, smbfs

(Note that NetBSD 3.0+ also use statvfs but with BSD syntax.)

For all other OSes we simply return 1.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>