Fix several C99 compatibility issues in the configure script.  Most
of them are specific to the uucp package.

Submitted upstream: <https://savannah.gnu.org/bugs/index.php?63647>

diff --git a/configure b/configure
index 4cced27226101612..77336b5f0a1ba20d 100755
--- a/configure
+++ b/configure
@@ -1280,7 +1280,7 @@ cat > conftest.$ac_ext << EOF
 #line 1281 "configure"
 #include "confdefs.h"
 
-main(){return(0);}
+int main(){return(0);}
 EOF
 if { (eval echo configure:1286: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then
   ac_cv_prog_cc_works=yes
@@ -3025,6 +3025,7 @@ else
   cat > conftest.$ac_ext <<EOF
 #line 3027 "configure"
 #include "confdefs.h"
+extern void exit ();
 
 int main() {
 extern void foo (); (void) exit (0);
@@ -3153,6 +3154,7 @@ else
   cat > conftest.$ac_ext <<EOF
 #line 3155 "configure"
 #include "confdefs.h"
+#include <string.h>
 
 int main() {
  char *i; int j, k; memset(i, j, k); 
@@ -3185,6 +3187,7 @@ else
   cat > conftest.$ac_ext <<EOF
 #line 3187 "configure"
 #include "confdefs.h"
+#include <string.h>
 
 int main() {
  char *i, *j; int k; memcmp(i, j, k); 
@@ -3217,6 +3220,7 @@ else
   cat > conftest.$ac_ext <<EOF
 #line 3219 "configure"
 #include "confdefs.h"
+#include <string.h>
 
 int main() {
  char *i, *j; int k; memcpy(i, j, k); 
@@ -3894,7 +3898,7 @@ else
 
 #include <sys/types.h>
 #include <sys/timeb.h>
-main ()
+int main ()
 {
   struct timeb s, slast;
   int c = 0;
@@ -3904,13 +3908,13 @@ main ()
       ftime (&s);
       if (s.time < slast.time
 	  || (s.time == slast.time && s.millitm < slast.millitm))
-	exit (1);
+	return 1;
       if (s.time != slast.time)
 	++c;
       slast.time = s.time;
       slast.millitm = s.millitm;
     }
-  exit (0);
+  return 0;
 }
 
 EOF
diff --git a/configure.in b/configure.in
index 452cf793f9ecc575..a788d07d123c7744 100644
--- a/configure.in
+++ b/configure.in
@@ -278,7 +278,7 @@ fi
 dnl
 AC_MSG_CHECKING(for void)
 AC_CACHE_VAL(uucp_cv_c_void,
-[AC_TRY_COMPILE([], [extern void foo (); (void) exit (0);],
+[AC_TRY_COMPILE([extern void exit ();], [extern void foo (); (void) exit (0);],
 uucp_cv_c_void=yes, uucp_cv_c_void=no)])
 AC_MSG_RESULT($uucp_cv_c_void)
 if test $uucp_cv_c_void = yes; then
@@ -318,7 +318,7 @@ dnl On some systems, memset, memcmp, and memcpy must be called with
 dnl the right number of arguments.
 AC_MSG_CHECKING(for memset)
 AC_CACHE_VAL(ac_cv_func_memset,
-[AC_TRY_LINK([], [ char *i; int j, k; memset(i, j, k); ],
+[AC_TRY_LINK([#include <string.h>], [ char *i; int j, k; memset(i, j, k); ],
 ac_cv_func_memset=yes, ac_cv_func_memset=no)])
 AC_MSG_RESULT($ac_cv_func_memset)
 if test $ac_cv_func_memset = yes; then
@@ -327,7 +327,7 @@ fi
 dnl
 AC_MSG_CHECKING(for memcmp)
 AC_CACHE_VAL(ac_cv_func_memcmp,
-[AC_TRY_LINK([], [ char *i, *j; int k; memcmp(i, j, k); ],
+[AC_TRY_LINK([#include <string.h>], [ char *i, *j; int k; memcmp(i, j, k); ],
 ac_cv_func_memcmp=yes, ac_cv_func_memcmp=no)])
 AC_MSG_RESULT($ac_cv_func_memcmp)
 if test $ac_cv_func_memcmp = yes; then
@@ -336,7 +336,7 @@ fi
 dnl
 AC_MSG_CHECKING(for memcpy)
 AC_CACHE_VAL(ac_cv_func_memcpy,
-[AC_TRY_LINK([], [ char *i, *j; int k; memcpy(i, j, k); ],
+[AC_TRY_LINK([#include <string.h>], [ char *i, *j; int k; memcpy(i, j, k); ],
 ac_cv_func_memcpy=yes, ac_cv_func_memcpy=no)])
 AC_MSG_RESULT($ac_cv_func_memcpy)
 if test $ac_cv_func_memcpy = yes; then
@@ -373,7 +373,7 @@ AC_CACHE_VAL(uucp_cv_sys_ftime_ok,
 [AC_TRY_RUN([
 #include <sys/types.h>
 #include <sys/timeb.h>
-main ()
+int main ()
 {
   struct timeb s, slast;
   int c = 0;
@@ -383,13 +383,13 @@ main ()
       ftime (&s);
       if (s.time < slast.time
 	  || (s.time == slast.time && s.millitm < slast.millitm))
-	exit (1);
+	return 1;
       if (s.time != slast.time)
 	++c;
       slast.time = s.time;
       slast.millitm = s.millitm;
     }
-  exit (0);
+  return 0;
 }
 ],
 uucp_cv_sys_ftime_ok=yes,