musl: exit on configure failure
perl: put manpages into man1perl/, man3perl/
man: update to latest
add manpp preprocessor to deal with groff junk and mdoc
busybox: build true and false as separate bins

that allows to make symlinks to /bin/true and false without
making busybox scream about unknown applets
for example
ln -s /bin/true /bin/makeinfo
would lead to "makeinfo: applet not found"

admittedly it's a bit of a hack to stuff this into the busybox package,
otoh it saves a lot of work to do it like this.