src: remove typedefs for structs

Remove all typedefs for structs, they were hiding the real type.
doc: update DoxyFile to doxygen ver 1.8.3.1
pfx: remove doxygen annotation for non-existent parameter

Remove documentation for parameter socket_id of pfx_table_remove(..).
The parameter socket_id doesn't exist anymore.
src: remove typedefs for enums

remove all typedefs for enum, they don't provide any benefit, only
hiding the real type
pfx: add missing doxygen documentation for function arg

add documentation for socket parameter of pfx_table_remove() function.
Merge branch 'develop' of https://github.com/rtrlib/rtrlib into develop

Conflicts:
	rtrlib/lib/ip.h
	rtrlib/pfx/lpfst/lpfst-pfx.c
	rtrlib/pfx/pfx.h
	rtrlib/rtr/packets.c
	rtrlib/rtr/packets.h
	rtrlib/rtr_mgr.c
	rtrlib/rtr_mgr.h
	tests/test_pfx.c
	tools/rtrclient.c