Revert "socketlib: properly fix the IPv6 to IPv4 fallback code."

This reverts commit 08477065972186327dba55ba0da92892c84b6c16, which
caused failures as reported in github issue #189. Hopefully this does
not break it for other users again...
Refactor and rewrite.

Perl script is removed in favour of C. Stale documentation and initfiles
are removed for now also.

C interface works, but still needs work (for example, mDNS is missing) -
see TODO.
rewrite: add mDNS registration
fix potential deadlock while shutting down
audio: output selection functionality
main: add option parsing
ao: add option parsing
cleanups
TODO updates

lots knocked off the list!
Add copyright notices.
usage: default buffer_start_fill was wrong
usage: usage of default buffer_start_fill was wrong
mdns: NULL-terminate argv lists
player: avoid leaking memory
generate hw_addr from apname
readability cleanup
ao: shutdown properly
Makefile: configure for libraries properly
ao: actually use the options we collect
rename arguments for compatibility with old version