SHA256 was chosen because it is reasonably standard, the file names
don't explode in length (this rules out SHA512) and it is supported by
basically all versions of OpenSSL (this rules out SHA512/256 and SHA3).
The protocol is changed in a backward compatible way: The supporting
server sends the SHA256 corresponding to the map in the `MAP_DETAILS`
message prior to sending the `MAP_CHANGE` message. The client saves the
SHA256 obtained from the `MAP_DETAILS` message until the next
`MAP_CHANGE` message.
For servers not supporting this protocol, the client falls back to
simply opening maps like in the previous scheme.
Remove the `map_version` tool, it is not being used and would have been
a little bit effort to update.
Use the OpenSSL implementation of SHA256 if it is supported, otherwise
fall back to a public domain one.
Fix#1127.
Replace `mem_free` by `free`, and `mem_alloc` by `malloc` or `calloc`
(the latter one being used to allocate a zeroed array of elements,
sometimes, this makes a call to `mem_zero` superfluous).
This results in having to remove `mem_stats` which previously recorded
the number of allocations and their size that the Teeworlds code did
directly.
Remove OOM handling in `src/game/client/components/binds.cpp`.
Remove needless copying in the CSV code in
`src/game/client/components/statboard.cpp`.
Also annotate `dbg_msg`, `str_format` and `str_timestamp_ex` so that the
compiler can determine whether the format strings are correct.
Fix the compiler warnings generated by these extra warnings -- some of
them were security issues.
CDataFileReader::Open(): Check the return status of io_read()
before reading the buffer, to avoid reading uninitialized data
in case the file was shorter than a full header.
CSkins::SkinScan(): Check that the image is high enough.
