Add chdir and getcwd and store cwd in the nfs_context.
Add functions to process the paths specified and normalize them
by performing the transforms :
// -> /
/./ -> /
^/../ -> error
^[^/] -> error
/string/../ -> /
/$ -> \0
/.$ -> \0
^/..$ -> error
/string/..$ -> /
Update the path lookup function to allow specifying relative paths based on
cwd for all functions.