Add a missing implied int in the Berkeley DB configure probe.  This
avoids build failures with future Fedora toolchain defaults.
 
Submitted upstream: <https://bz.apache.org/bugzilla/show_bug.cgi?id=66396>

diff --git a/build/dbm.m4 b/build/dbm.m4
index 57bd131fc3b74099..ffdbdbc0f43e04da 100644
--- a/build/dbm.m4
+++ b/build/dbm.m4
@@ -235,7 +235,7 @@ AC_DEFUN([APU_TRY_BERKELEY_DB],
 #include <stdlib.h>
 #include <stdio.h>
 #include <$apu_try_berkeley_db_header>
-main ()
+int main ()
 {
   int major, minor, patch;