Avoid implicit function declarations because they have been removed
from C in 1999.  Future compilers are likely to reject them by
default.

No need to upstream this because the aclocal.m4 file is not checked
into the repository since:

------------------------------------------------------------------------
r412 | clasen | 1999-11-06 14:10:34 +0100 (Sat, 06 Nov 1999) | 3 lines
Changed paths:
   M /trunk/sp/Makefile.in
   D /trunk/sp/config/aclocal.m4
   D /trunk/sp/config/configure.in
   M /trunk/sp/configure
   A /trunk/sp/configure.in

Install headers in $(includedir)/OpenSP, move configure.in to toplevel,
remove generated file aclocal.m4.

diff --git a/aclocal.m4 b/aclocal.m4
index d7cc45cf7b80ca54..2fde71fb866f12bc 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -833,10 +833,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -850,7 +846,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }]
 EOF
   if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext} 2>/dev/null; then
diff --git a/configure b/configure
index caa2d31585b112bd..90dce8e854b35393 100755
--- a/configure
+++ b/configure
@@ -2917,7 +2917,7 @@ if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
   echo "$as_me:$LINENO: \$? = $ac_status" >&5
   (exit $ac_status); }; }; then
   for ac_declaration in \
-   '' \
+   '#include <stdlib.h>' \
    'extern "C" void std::exit (int) throw (); using std::exit;' \
    'extern "C" void std::exit (int); using std::exit;' \
    'extern "C" void exit (int) throw ();' \
@@ -5186,8 +5186,8 @@ main ()
   for (i = 0; i < 256; i++)
     if (XOR (islower (i), ISLOWER (i))
 	|| toupper (i) != TOUPPER (i))
-      exit(2);
-  exit (0);
+      return 2;
+  return 0;
 }
 _ACEOF
 rm -f conftest$ac_exeext
@@ -9508,10 +9508,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -9525,7 +9521,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9606,10 +9602,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -9623,7 +9615,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -13321,10 +13313,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -13338,7 +13326,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -13419,10 +13407,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -13436,7 +13420,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -19110,10 +19094,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -19127,7 +19107,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -19208,10 +19188,6 @@ else
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -19225,7 +19201,7 @@ int main ()
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -27450,8 +27426,8 @@ main ()
   for (i = 0; i < 256; i++)
     if (XOR (islower (i), ISLOWER (i))
 	|| toupper (i) != TOUPPER (i))
-      exit(2);
-  exit (0);
+      return 2;
+  return 0;
 }
 _ACEOF
 rm -f conftest$ac_exeext