external/wakaama: update core APIs to support TCP/TLS as per RFC

external/wakaama: update core APIs to support TCP/TLS as per RFC

This commit is related to er-coap TCP/TLS support according to changes
of wakaama er-coap API, updates wakaama core APIs to support TCP/TLS
feature.
 - lwm2m_context_t : added new member, coap_protocol_t protocol
 - lwm2m_init2 function is newly added to intialize
   coap protocol member in lwm2m_context_t
 - transaction_new : added new argument, coap_protocol_t proto
 - lwm2m_buffer_send : added new argument, coap_protocol_t proto
 - core functions using coap_init_message, coap_parse_message
   are updated

Change-Id: Icc7e3a7ac64e703255aafbab6c3f3d04dbb82cb4
Signed-off-by: Jin-Seong Kim <jseong82.kim@samsung.com>