adjust CFLAGS detection

gen compat for getprogname

rework the configless mode: change flags and generate certs

fixing compat compilation include headers if needed and include config.h

missing ; in prototype

add missing getprogname test + eventually include err.h

more OpenBSD goodies

simplify CFLAGS/LDFLAGS autodetection


add a configure script and some compat tested on openbsd, alpine and void