NFS: replace ino_t with u_int32_t (GH #335 pt. 1)

NFS file handle is an opaque server-issued sequence of bytes. Parse_fh()
function implements heuristics to decode file handles generated by some
NFS servers, among other information extracting the node (inode) number.
It decodes only 32-bit node numbers.

NFS implementations use ino_t C type to represent the node number. The
type size may vary across implementations/encodings and may be missing
during compile time.

Tcpdump used to have its own typedef for ino_t. Gisle Vanem points that
it caused a problem with MSVC v.16.00.40219.01 for 80x86, which defines
the same type in <sys/types.h>. This change fixes tcpdump code to use
u_int32_t and removes the typedef.