Add --disable-embedded-cryptopp to warp buildslave

[midnightmagic]

As you can see here:

​http://tahoe-lafs.org/buildbot-pycryptopp/builders/MM%20netbsd5%20i386%20warp/builds/39/steps/test/logs/stdio

... it looks like with a system crypto++ installed (in my case, 5.6.1) there are pieces pulled in from the crypto++ 5.6.1 header files which reference a CryptoPP:: function which does not exist in the embedded version, which therefore causes the test to fail.

The fix appears to be to tell (as I suspect you were going to anyway) setup.py to disable the embedded cryptopp stuff.