Add the necessary 'strip' commands to the BSD/OS section of configure because

BSD/OS does not like shared libraries without a symbol table and gives errors
when linking against libavcodec.so otherwise.
patch by Steven M. Schultz < sms == at == 2BSD == dot == COM >

Originally committed as revision 4722 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -323,6 +323,8 @@ audio_oss="yes"
 dv1394="no"
 extralibs="-lpoll -lgnugetopt -lm"
 make="gmake"
+strip="strip -d"
+installstrip=""
 ;;
 Darwin)
 cc="cc"