Upgrade to PEAR2_HTTP_Request master with proxy fix

The commit b69c1c34 which was to include v0.3.1 actually added v0.3.0

There is no v0.3.1 tag (in git), but the master branch of
PEAR2_HTTP_Request does include the fix for proxy support.

Master branch from PEAR2_HTTP_Request (https://github.com/pear2/HTTP_Request)
that is being added is at a877196f6e from 2012-02-21.

Signed-off-by: Paul Campbell <paulcampbell@fife.ac.uk>