Document the UI utility functions

=pod

=head1 NAME

UI_UTIL_read_pw_string, UI_UTIL_read_pw,

*UI_UTIL_wrap_read_pem_callback - user interface utilities

=head1 SYNOPSIS

 #include <openssl/ui.h>

 int UI_UTIL_read_pw_string(char *buf, int length, const char *prompt,

                            int verify);

 int UI_UTIL_read_pw(char *buf, char *buff, int size, const char *prompt,

                     int verify);

 UI_METHOD *UI_UTIL_wrap_read_pem_callback(pem_password_cb *cb, int

 rwflag);

=head1 DESCRIPTION

UI_UTIL_read_pw_string() asks for a passphrase, using B<prompt> as a

prompt, and stores it in B<buf>.

The maximum allowed size is given with B<length>, including the

terminating NUL byte.

If B<verify> is non-zero, the password will be verified as well.

UI_UTIL_read_pw() does the same as UI_UTIL_read_pw_string(), the

difference is that you can give it an external buffer B<buff> for the

verification passphrase.

UI_UTIL_wrap_read_pem_callback() can be used to create a temporary

B<UI_METHOD> that wraps a given PEM password callback B<cb>.

B<rwflag> is used to specify if this method will be used for

passphrase entry without (0) or with (1) verification.

When not used any more, the returned method should be freed with

UI_destroy_method().

=head1 COPYRIGHT

Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use

this file except in compliance with the License.  You can obtain a copy

in the file LICENSE in the source distribution or at

L<https://www.openssl.org/source/license.html>.

=cut