add sccp_utils.h to Makefile.am
add sccp_device prefix to functions working on sccp_device
remove check for device null on sccp_device_* functions
move device_type_str in sccp_message.c
move line_state_str in sccp_message.c
rename *_str functions
more sccp_ prefix
don't use default case when using all cases of an enum
rename sccp_new_line to sccp_line_create
remove check for line null on sccp_line_* functions
update unit tests
update name of sccp_config functions
update null checks on sccp_config functions