Update pear-Net_SMTP package to 1.5.2.

1.5.2 (stable) 2011-04-17 02:29 UTC

- Avoid requesting immediate socket timeouts. (Bug 18335)
- Added support for passing additional socket options. (Request 18418)

1.5.1 (stable) 2011-03-11 06:27 UTC

- Fixing SASL proxy authentication for DIGEST-MD5. (Bug 17538)
- Fixing the default socket timeout. (Bug 18335)

1.5.0 (stable) 2011-02-07 04:11 UTC

- Avoid appending an extra space in mailFrom() when $params is empty. (Bug
  17989)
- Differentiating between a connection timeout and general socket I/O
  timeouts. (Request 18197)

(taca)