Fix:
error: implicit declaration of function 'to_upper' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
--- echoping.h.orig	2007-04-05 07:40:49.000000000 -0500
+++ echoping.h	2020-11-24 18:57:56.000000000 -0600
@@ -208,6 +208,7 @@
 void tvstddevavg ();
 double tv2double ();
 struct timeval double2tv ();
+char *to_upper(char *input);
 /* http.c */
 #ifdef HTTP
 char *make_http_sendline ();
--- configure.orig	2007-04-09 14:53:04.000000000 -0500
+++ configure	2020-11-25 04:28:58.000000000 -0600
@@ -8958,7 +8958,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9058,7 +9058,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
--- plugins/configure.orig	2007-04-09 14:55:12.000000000 -0500
+++ plugins/configure	2020-11-25 04:28:58.000000000 -0600
@@ -8948,7 +8948,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9048,7 +9048,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
--- plugins/dns/configure.orig	2007-04-09 14:55:24.000000000 -0500
+++ plugins/dns/configure	2020-11-25 04:28:58.000000000 -0600
@@ -8945,7 +8945,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9045,7 +9045,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
--- plugins/ldap/configure.orig	2007-04-09 14:55:36.000000000 -0500
+++ plugins/ldap/configure	2020-11-25 04:28:58.000000000 -0600
@@ -8945,7 +8945,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9045,7 +9045,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
--- plugins/postgresql/configure.orig	2007-04-09 14:55:47.000000000 -0500
+++ plugins/postgresql/configure	2020-11-25 04:28:58.000000000 -0600
@@ -8946,7 +8946,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9046,7 +9046,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
--- plugins/random/configure.orig	2007-04-09 14:55:59.000000000 -0500
+++ plugins/random/configure	2020-11-25 04:28:58.000000000 -0600
@@ -8942,7 +8942,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9042,7 +9042,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
--- plugins/whois/configure.orig	2007-04-09 14:56:10.000000000 -0500
+++ plugins/whois/configure	2020-11-25 04:28:58.000000000 -0600
@@ -8944,7 +8944,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -9044,7 +9044,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+  return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5