* HTTP.{cpp,h} : move length() method to base class

HTTP.cpp

@@ -279,7 +279,7 @@ namespace http {
     return false;
   }
 
-  long int HTTPRes::length() {
+  long int HTTPMsg::length() {
     unsigned long int length = 0;
     auto it = headers.find("Content-Length");
     if (it == headers.end())

HTTP.h

@@ -59,6 +59,9 @@ namespace http {
 
     void add_header(const char *name, const char *value, bool replace = false);
     void del_header(const char *name);
+
+    /** @brief Returns declared message length or -1 if unknown */
+    long int length();
   };
 
   struct HTTPReq : HTTPMsg {
@@ -113,9 +116,6 @@ namespace http {
 
     /** @brief Checks that response declared as chunked data */
     bool is_chunked();
-
-    /** @brief Returns declared response length or -1 if unknown */
-    long int length();
   };
 
   /**