The SEI message read/write functions are called
via function pointers where the SEI message-specific
context is passed as void*. But the actual function
definitions use a pointer to their proper context
in place of void*, making the calls undefined behaviour.
Clang UBSan 17 warns about this.

This commit fixes this by adding wrapper functions
(created via macros) that have the right type that
call the actual functions. This reduced the number of failing
FATE tests with UBSan from 164 to 85 here.
Reviewed-by: Mark Thompson <sw@jkqxz.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>