A rewrite of the error handling in the libsmb client code. I've separated

A rewrite of the error handling in the libsmb client code.  I've separated
out the error handling into a bunch of separate functions rather than all
being handled in one big function.

Fetch error codes from the last received packet:

    void cli_dos_error(struct cli_state *cli, uint8 *eclass, uint32 *num);
    uint32 cli_nt_error(struct cli_state *);

Convert errors to UNIX errno values:

    int cli_errno_from_dos(uint8 eclass, uint32 num);
    int cli_errno_from_nt(uint32 status);
    int cli_errno(struct cli_state *cli);

Detect different kinds of errors:

    BOOL cli_is_dos_error(struct cli_state *cli);
    BOOL cli_is_nt_error(struct cli_state *cli);
    BOOL cli_is_error(struct cli_state *cli);

This also means we now support CAP_STATUS32 as we can decode and understand
NT errors instead of just DOS errors.  Yay!

Ported a whole bunch of files in libsmb to use this new API instead of the
just the DOS error.