fix building main.cpp when readline is available

This changes around the pragma conditionals to make sure that certain
symbols (such as "default_search_path") are defined even if the system
has readline available during builds.

src/main.cpp

@@ -23,6 +23,18 @@ char *mystrdup (const char *s) {
     return d;                            // Return the new string
 }
 
+char* readline(const char* p)
+{
+  std::string retval;
+  std::cout << p ;
+  std::getline(std::cin, retval);
+  return std::cin.eof() ? NULL : mystrdup(retval.c_str());
+}
+
+void add_history(const char*){}
+void using_history(){}
+#endif
+
 void *cast_module_symbol(std::string (*t_path)())
 {
   union cast_union
@@ -101,19 +113,6 @@ std::string default_search_path()
 #endif
 }
 
-
-char* readline(const char* p)
-{
-  std::string retval;
-  std::cout << p ;
-  std::getline(std::cin, retval);
-  return std::cin.eof() ? NULL : mystrdup(retval.c_str());
-}
-
-void add_history(const char*){}
-void using_history(){}
-#endif
-
 void help(int n) {
   if ( n >= 0 ) {
     std::cout << "ChaiScript evaluator.  To evaluate an expression, type it and press <enter>." << std::endl;