This commit adds tests to check the behavior of the record encryption
routine `ssl_encrypt_buf` when the buffer surrounding the plaintext is
too small to hold the expansion in the beginning and end (due to IV's,
padding, and MAC).
Each test starts successively increases the space available at the
beginning, end, or both, of the record buffer, and checks that the
record encryption either fails with a BUFFER_TOO_SMALL error, or
that it succeeds. Moreover, if it succeeds, it is checked that
decryption succeeds, too, and results in the original record.
This commit adds tests exercising mutually inverse pairs of
record encryption and decryption transformations for the various
transformation types allowed in TLS: Stream, CBC, and AEAD.
Add a test case calling ssl_set_hostname twice to test_suite_ssl.
When run in CMake build mode ASan, this catches the current leak,
but will hopefully be fine with the new version.
