This commit introduces source files
- `ssl_12_gen.c`
- `ssl_12_srv.c`
- `ssl_12_cli.c`
which will subsequently be populated with implementations
for handshake reading and writing functions for all TLS
versions <= 1.2. `ssl_12_gen.c` shall contain functions
shared between client and server, while `ssl_12_cli.c`
and `ssl_12_srv.c` shall contain client/server-specific
functions only.
In order to retain git history, those files are so far
identical copies of `ssl_tls.c`, `ssl_srv.c` and `ssl_cli.c`,
and those latter files have been moved to temporary files
`ssl_xxx_old.c`. Subsequent commits will rename them back
to their original name and do the actual code split.
This commit is the first step in implementing the TLS handshake logic
and the low-level (D)TLS messaging functionality (record layer and
retransmission state machine) in separate source files. So far, they're
both implemented in ssl_tls.c.
To begin, this commit creates unmodified copies ssl_tls_old.c and ssl_msg.c
of ssl_tls.c, which in turn is deleted. Subsequent commits will then rename
ssl_tls_old.c back into ssl_tls.c and remove code so that each piece of
functionality is contained in precisely one of ssl_tls.c or ssl_msg.c.
This approach allows to maintain the git line history.
