Fix msvc compile error and improve 64 bit compatibility
Merge pull request #973 from cgohlke/patch-1

Fix msvc compile error and improve 64 bit compatibility
Add a new TORNADO_EXTENSION environment variable for testing purposes.

This variable can be set to 0 to suppress or 1 to require the use of the
extension (instead of the default to use it when it is available but silently
fall back).  Require the extension to be present on travis-ci.
Add better debugging for ImportErrors resulting from TORNADO_EXTENSION=1
Reinstate the 'cd maint' in .travis.yml.

This turned out to be breaking the speedups module.
Don't require the extension to be present when building docs.
Add SystemError to errors from compilation

OSX generates a SystemError from a missing compiler; trap with other
compilation errors.
Merge branch 'stable' into branch3.2
Add versioning parameters to secure_cookie/signed_value APIs.
Add a v2 secure cookie format.

This format fixes some weaknesses in the original format that would allow
characters to be shifted from the "value" field to the "name" or "timestamp"
fields.  It also upgrades the signature from HMAC-SHA1 to HMAC-SHA256,
adds an explicit version field, and adds an as-yet-unused field to
support key rotation in the future.
Document the cookie versioning interface.
v3.2.1 release notes
Set version number to 3.2.1