Add a configure option to opt-out secure memory
./config -DOPENSSL_NO_SECURE_MEMORY
#include <string.h>
/* e_os.h includes unistd.h, which defines _POSIX_VERSION */
-#if defined(OPENSSL_SYS_UNIX) \
+#if !defined(OPENSSL_NO_SECURE_MEMORY) && defined(OPENSSL_SYS_UNIX) \
&& defined(_POSIX_VERSION) && _POSIX_VERSION >= 200112L
# define IMPLEMENTED
# include <stdlib.h>
