Fixed FreeBDS xpg4 check.

diff --git a/configure.in b/configure.in
index f39afbb..f3066bc 100644
--- a/configure.in
+++ b/configure.in
@@ -104,7 +104,7 @@
 dnl Check for -lsocket for Solaris
 AC_CHECK_FUNCS(connect,,AC_CHECK_LIB(socket,connect))
 dnl Check for -lxpg4 for FreeBSD
-AC_CHECK_LIB(xpg4,setrunelocale)
+AC_CHECK_LIB(xpg4,_xpg4_setrunelocale)
 dnl Check for -lmmap for OS/2
 AC_CHECK_LIB(mmap,mmap)
 dnl Check for openpty