fix emulated inet_aton so that it fails for invalid addresses

patch by elupus: \elupus ecce se/
original thread:
[FFmpeg-devel] [PATCH] emulated inet_aton doesn't fail for invalidaddresses
date: 07/15/2007 12:40 AM

Originally committed as revision 9731 to svn://svn.ffmpeg.org/ffmpeg/trunk