Patch for smbclient command du, tar cn, PASSWD_FILE and PASSWD_FD

[Andrew Tridgell]

> Perhaps we should #define REPLACE_GETPASS by default, until we find a
> work-around.

only on systems that have the necessary headers for our replacement
getpass code to work. 

in fact, maybe should just have a configure test to see if the 
getpass code compiles, and if it does then use it, otherwise use the
system one.