Improve readability of some code. No functional changes.
Improve readability of some code. No functional changes.

* buckets/ssl_buckets.c
  (bio_bucket_read,
   bio_bucket_write): Don't use ctx->bio and bio. They point to the same
     variable and mixing them only obfuscates this already hard to read
     code.

  (ssl_decrypt,
   ssl_encrypt): Document that these functions implement serf_databuf_reader_t.

jandre/serf,jandre/serf,jandre/serf,jandre/serf