BUG/MEDIUM: ssl: fix several bad pointer aliases in a few sample fetch functions

BUG/MEDIUM: ssl: fix several bad pointer aliases in a few sample fetch functions

Sample fetch functions ssl_x_sha1(), ssl_fc_npn(), ssl_fc_alpn(),
ssl_fc_session_id(), as well as the CLI's "show cert details" handler
used to dereference the output buffer's <data> field by casting it to
"unsigned *". But while doing this could work before 1.9, it broke
starting with commit 843b7cbe9d ("MEDIUM: chunks: make the chunk struct's
fields match the buffer struct") which merged chunks and buffers, causing
the <data> field to become a size_t. The impact is only on 64-bit platform
and depends on the endianness: on little endian, there should never be any
non-zero bits in the field as it is supposed to have been zeroed before the
call, so it shouldbe harmless; on big endian, the high part of the value
only is written instead of the lower one, often making the result appear
4 billion times larger, and making such values dropped everywhere due to
being larger than a buffer.

It seems that it would be wise to try to re-enable strict-aliasing to
catch such errors.

This must be backported till 1.9.