use generic sed test so this works on autoconf 2.59

ChangeLog

@@ -1,3 +1,9 @@
+2007-02-06  Greg Troxel  <Greg Troxel <gdt@ir.bbn.com>>
+
+	* configure.ac: Use generic sed test, since autoconf 2.59 lacks
+	AC_PROG_SED and while 2.59 is somewhat crufty, it isn't officially
+	crufty.
+
 2007-02-06  Greg Troxel  <Greg Troxel <gdt@ir.bbn.com>
 
 	* bootstrap.sh: use -i to install missing files

configure.ac

@@ -64,7 +64,10 @@ AC_PROG_CC
 AC_PROG_CPP
 
 AC_PROG_EGREP
-AC_PROG_SED
+
+dnl autoconf 2.59 appears not to support AC_PROG_SED
+dnl AC_PROG_SED
+AC_CHECK_PROG([SED],[sed],[sed],[/bin/false])
 
 dnl ------------------------------------------------------------------
 dnl Intel compiler check. Although Intel tries really hard to make icc