fftw: changed to use var_append() to add extra configure options

multimedia/fftw/fftw.conf

@@ -16,8 +16,8 @@
 
 # Optimization
 if [ $arch_machine = i686 -o $arch_machine = i586 -o $arch_machine = i486 -o $arch_machine = Intel -o $arch_machine = k6 -o $arch_machine = k7 ] ; then
-        confopt="$confopt --enable-i386-hacks"
+        var_append extraconfopt ' ' '--enable-i386-hacks'
         echo_status "Enable i386 hacks"
 fi
 
-confopt="$confopt --enable-threads"
+var_append extraconfopt ' ' '--enable-threads'