Build failure due to implicit declaration of functions

xine-lib 1.2.11 and xine-ui 0.99.13 don't make the correct determinations at configure time and (in the case of xine-ui) fail to build due to implicit declaration of functions for me on macOS 10.15.7.

The fix for xine-lib is here:

https://github.com/macports/macports-ports/blob/14fac26169652357b2e34bddf60877c7f33f286b/multimedia/xine-lib/files/implicit.patch

The fix for xine-ui is here:

https://github.com/macports/macports-ports/blob/f925ff1a4f8d59a40735ff52dc486d4b89a7c8c8/multimedia/xine-ui/files/implicit.patch

This also includes an unrelated typo fix in a configure message (allowes -> allows).

I also made one change in network.c that was not needed for macOS but is presumably needed for Sun: changing __sun__ to __sun to match what's in the other files; I assume that was just a typo.

My changes are to the configure script so as to avoid requiring MacPorts to run autoconf. Of course for your purposes you'll want to modify configure.ac or some .m4 file and I trust you can make the necessary adaptations.