Update pear-Net_SMTP to 1.7.1.

1.7.1
Release date: 2015-09-07 18:05 UTC
Changelog:

- Fix a syntax error in the quotedata() test.
- Fix an undefined value resulting from a bad merge. (#23)
- Add TLSv1.1 and TLSv1.2 support for STARTTLS connections. (#22)

1.7.0
Release date: 2015-09-06 19:20 UTC
Changelog:

- This version drops PHP 4 support in favor of more modern PHP language
  constructs.

(taca)