Split out some stuff that is shared between request and response

I now have files with the infinitely imaginative names
requestrespons.{c,h,test.c}.

tests/request.test.c

@@ -1,4 +1,8 @@
+#ifndef REQUEST_TEST
+#define REQUEST_TEST
+
 #include "munit/munit.h"
+#include "../src/readline.c"
 #include "../src/request.c"
 
 typedef struct {
@@ -160,3 +164,4 @@ int main (int argc, char* argv[]) {
 }
 
 #endif /* ifndef MAINTEST */
+#endif /* ifndef REQUEST_TEST */