patch 9.0.0834: warning for missing return type

Problem:    Warning for missing return type.
Solution:   Add "int". (San James, closes #11496)
diff --git a/src/configure.ac b/src/configure.ac
index e63c685..16ecd10 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3654,7 +3654,7 @@
 AC_MSG_CHECKING(for struct sigcontext)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([
 #include <signal.h>
-test_sig()
+int test_sig()
 {
     struct sigcontext *scont;
     scont = (struct sigcontext *)0;