Fix non C99 compliant check.

https://sourceforge.net/p/coan2/bugs/95/

diff --git a/configure.ac b/configure.ac

index 23ba6f0..13e6647 100644

--- configure.ac

+++ configure.ac

@@ -4,7 +4,7 @@ AC_PREREQ(2.59)

 AM_INIT_AUTOMAKE(1.13 no-define)

 AC_CHECK_HEADERS(strings.h)

 AC_MSG_CHECKING(for big-endian host)

-AC_TRY_RUN([main () {

+AC_TRY_RUN([int main () {

   /* Are we little or big endian?  From Harbison&Steele.  */

   union

   {

@@ -12,7 +12,7 @@ AC_TRY_RUN([main () {

     char c[sizeof (long)];

   } u;

   u.l = 1;

-  exit (u.c[sizeof (long) - 1] == 1);

+  return u.c[sizeof (long) - 1] == 1;

 }], BIG_ENDIAN=no, BIG_ENDIAN=yes)

 AC_MSG_RESULT([$BIG_ENDIAN])

 AM_CONDITIONAL([IS_BIG_ENDIAN],[test "$BIG_ENDIAN" = "yes"])