malloc + memset 0 -> calloc
(not that it matters much as this is in disabled code, for we don't build with
zlib support)
Mostly gut e_os.h:
USE_SOCKETS is unrelated to using sockets, but just pulls in .h files.  It
makes every file buy a kitchen sink, because 11 files forgot to.
EXIT() is really exit(), a gentle surprise
but... OPENSSL_EXIT() is really just return(), because noone compiles the
openssl command non-monolithic anymore