TODO

use wrapper framework to ensure CFLAGS and CXXFLAGS are honoured
fix ctype usage (unsigned char is the value range, not char or int)
add missing headers, e.g. string.h (important for LP64)
check configure tests for bultins and C99 macros, enforce link tests
check packages for builtin versions of libffi, boehm-gc, expat, zlib, tiff, ...
configure scripts should not check for entries in /dev, e.g. to detect bpf(4) or tun(4)
kill authors who write configure checks and don't use the results
interpreter check still doesn't catch all cases (e.g. xorg-server had missing Perl replacement)