Merge branch 'nd/warn-more-for-devs'

The build procedure "make DEVELOPER=YesPlease" learned to enable a bit more warning options depending on the compiler used to help developers more. There also is "make DEVOPTS=tokens" knob available now, for those who want to help fixing warnings we usually ignore, for example. * nd/warn-more-for-devs: Makefile: add a DEVOPTS to get all of -Wextra Makefile: add a DEVOPTS to suppress -Werror under DEVELOPER Makefile: detect compiler and enable more warnings in DEVELOPER=1 connect.c: mark die_initial_contact() NORETURN