Added a test to figure out if iconv() takes a const char **.

configure.in

@@ -405,6 +405,30 @@ AC_SEARCH_LIBS(inet_ntop, resolv)
 # Search for libiconv_open (not iconv_open) to discover if -liconv is needed!
 AC_SEARCH_LIBS(libiconv_open, iconv)
 
+if test "$am_cv_func_iconv" = yes; then
+    AC_MSG_CHECKING([for iconv declaration])
+    AC_CACHE_VAL(am_cv_proto_iconv, [
+      AC_TRY_COMPILE([
+#include <stdlib.h>
+#include <iconv.h>
+extern
+#ifdef __cplusplus
+"C"
+#endif
+#if defined(__STDC__) || defined(__cplusplus)
+size_t iconv (iconv_t cd, char * *inbuf, size_t *inbytesleft, char * *outbuf, size_t *outbytesleft);
+#else
+size_t iconv();
+#endif
+], [], am_cv_proto_iconv_arg1="", am_cv_proto_iconv_arg1="const")
+      am_cv_proto_iconv="extern size_t iconv (iconv_t cd, $am_cv_proto_iconv_arg1 char * *inbuf, size_t *inbytesleft, char * *outbuf, size_t *outbytesleft);"])
+    am_cv_proto_iconv=`echo "[$]am_cv_proto_iconv" | tr -s ' ' | sed -e 's/( /(/'`
+    AC_MSG_RESULT([$]{ac_t:-
+         }[$]am_cv_proto_iconv)
+    AC_DEFINE_UNQUOTED(ICONV_CONST, $am_cv_proto_iconv_arg1,
+      [Define as const if the declaration of iconv() needs const.])
+fi
+
 dnl AC_MSG_NOTICE([Looking in libraries: $LIBS])
 
 AC_CHECK_FUNCS(inet_ntop, , [AC_LIBOBJ(lib/inet_ntop)])