databases/libcouchbase: 2.6.2 -> 2.6.3

• WWW changed from https://github.com/couchbase/libcouchbase/ to http://developer.couchbase.com/documentation/server/current/sdk/c/start-using-sdk.html

PR: 213040
Changes: https://github.com/couchbase/libcouchbase/blob/master/RELEASE_NOTES.markdown
Submitted by: Sergey Avseyev <sergey.avseyev@gmail.com> (maintainer)