ddb(4): db_read_bytes/db_write_bytes: change dst/src parameter to void*

ddb(4): db_read_bytes/db_write_bytes: change dst/src parameter to void*

Almost all db_read_bytes() callers cast the destination buffer
argument to char*, which suggests the API's prototype is incompatible
with how the API is actually used.

Change db_read_bytes() and db_write_bytes() to take a void* as the
destination/source buffer parameter so callers don't need to cast the
argument.

With input from bluhm@.  Bugs caught by Clemens Gossnitzer (ASCII
approximation of name).

Thread: https://marc.info/?l=openbsd-tech&m=170740813021636&w=2

ok bluhm@