Installation should be more intelligent regarding LCB requirements

Python 2.4.0 onwards relies on Libcouchbase 2.9.0+, if you try to install Python 2.4.0 with an earlier Libcouchbase you get warnings about crypto methods:

 src/crypto.c: In function 'pycbc_crypto_exc_wrap_v1_encrypt':

  src/crypto.c:708:42: error: 'union <anonymous>' has no member named 'v1'; did you mean 'v0'?

           lcb_result = orig_lcb_provider->v.v1.encrypt(orig_lcb_provider,

                                            ^

  src/crypto.c: In function 'pycbc_crypto_exc_wrap_v1_decrypt':

  src/crypto.c:742:42: error: 'union <anonymous>' has no member named 'v1'; did you mean 'v0'?

           lcb_result = orig_lcb_provider->v.v1.decrypt(orig_lcb_provider,

                                            ^

These errors are pretty cryptic unless you're in the know about what features were added to which SDK when.

It would be a much better experience for everyone if any time we had to bump the minimum libcouchbase dependency we could have some installation-level check saying something like:

Libcouchbase 2.9.0 required, version 2.8.2 found. Please update libcouchbase to a later version before installing this version of the Python SDK.

This is a clear error message for the user, with clear instructions for how to resolve their issue.

As an aside https://developer.couchbase.com/server/other-products/release-notes-archives/python-sdk does not cover the need for a minimum version of Libcouchbase.