Index: ogg.m4
===================================================================
--- ogg.m4.orig
+++ ogg.m4
@@ -20,7 +20,7 @@ AC_ARG_ENABLE(oggtest,AC_HELP_STRING([--
     OGG_LIBS=""
   elif test "x$ogg_prefix" != "x" ; then
     OGG_LIBS="-L$ogg_prefix/lib"
-  elif test "x$prefix" != "xNONE" ; then
+  elif test "x$prefix" != "xNONE" -a "x$prefix" != "x/usr"; then
     OGG_LIBS="-L$prefix/lib"
   fi
 
@@ -34,7 +34,7 @@ AC_ARG_ENABLE(oggtest,AC_HELP_STRING([--
     OGG_CFLAGS=""
   elif test "x$ogg_prefix" != "x" ; then
     OGG_CFLAGS="-I$ogg_prefix/include"
-  elif test "x$prefix" != "xNONE"; then
+  elif test "x$prefix" != "xNONE" -a "x$prefix" != "x/usr"; then
     OGG_CFLAGS="-I$prefix/include"
   fi
 
@@ -62,7 +62,7 @@ dnl
 #include <string.h>
 #include <ogg/ogg.h>
 
-int main ()
+int main (void)
 {
   system("touch conf.oggtest");
   return 0;