ngap_common.h is for common IEs enc/dec functions, utilities
should go into a separate file. Changes in this commit:
* Add ngap_utils.h (utilities)
* Move helper macros (NGAP_ERROR, NGAP_DEBUG, NGAP_FIND_PROTOCOLIE_BY_ID, etc.) to ngap_utils.h
* Move equality check macros (_NGAP_EQ_CHECK_*) to ngap_utils.h
* Clean up includes
This change is preparatory to the introduction the paging lib with unit
tests, with the goal of reducing the inter-dependency between concurrent
NGAP libs.