This implements the changes discussed in #68 and #72.
This breaks compatibility with the previous AES implementation.
This also fixes two problems reported by valgrind:
==4887== Invalid write of size 2
==4887== at 0x483E9DB: memmove (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4887== by 0x10E37F: setup_aes_key (transform_aes.c:378)
==4887== by 0x10E451: add_aes_key (transform_aes.c:401)
==4887== by 0x10ED10: transop_aes_setup_psk (transform_aes.c:580)
==4887== by 0x10A547: main (benchmark.c:92)
==4887== Address 0x4d574a0 is 0 bytes after a block of size 16 alloc'd
==4887== at 0x4839B65: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4887== by 0x10E337: setup_aes_key (transform_aes.c:374)
==4887== by 0x10E451: add_aes_key (transform_aes.c:401)
==4887== by 0x10ED10: transop_aes_setup_psk (transform_aes.c:580)
==4887== by 0x10A547: main (benchmark.c:92)
==13057== Use of uninitialised value of size 8
==13057== at 0x49023B3: ??? (in /usr/lib/libcrypto.so.1.1)
==13057== by 0x490346A: AES_cbc_encrypt (in /usr/lib/libcrypto.so.1.1)
==13057== by 0x11270A: transop_encode_aes (transform_aes.c:230)
==13057== by 0x10F5CD: send_packet2net (edge_utils.c:1224)
==13057== by 0x10F813: readFromTAPSocket (edge_utils.c:1278)
==13057== by 0x1106A8: run_edge_loop (edge_utils.c:1596)
==13057== by 0x10B9F7: main (edge.c:701)
