polarssl: build with PolarSSL-1.0.0

With this fix, it should work for PolarSSL-1.0.0 (and SVN-1091 trunk)
and retain compatibility with earlier versions. (Tested with 0.14.1)

PolarSSL still doesn't play nicely with curl's CA bundle (we discussed
this before) but I was at least able to retrieve the
https://www.gmail.com/ login page using a modified ca-certificates.crt
file with all 3 versions of PolarSSL.