cleaned up Curl_write() and the sub functions it uses for various protocols.

They all now return ssize_t to Curl_write().

Unfortunately, Curl_read() is in a sorrier state but it too would benefit from
a similar cleanup.

lib/sslgen.c

@@ -455,10 +455,10 @@ struct curl_slist *Curl_ssl_engines_list(struct SessionHandle *data)
 }
 
 /* return number of sent (non-SSL) bytes */
-int Curl_ssl_send(struct connectdata *conn,
-                  int sockindex,
-                  void *mem,
-                  size_t len)
+ssize_t Curl_ssl_send(struct connectdata *conn,
+                      int sockindex,
+                      void *mem,
+                      size_t len)
 {
 #ifdef USE_SSLEAY
   return Curl_ossl_send(conn, sockindex, mem, len);
@@ -481,10 +481,10 @@ int Curl_ssl_send(struct connectdata *conn,
  * If the read would block (EWOULDBLOCK) we return -1. Otherwise we return
  * a regular CURLcode value.
  */
-int Curl_ssl_recv(struct connectdata *conn, /* connection data */
-                  int sockindex,            /* socketindex */
-                  char *mem,                /* store read data here */
-                  size_t len)               /* max amount to read */
+ssize_t Curl_ssl_recv(struct connectdata *conn, /* connection data */
+                      int sockindex,            /* socketindex */
+                      char *mem,                /* store read data here */
+                      size_t len)               /* max amount to read */
 {
 #ifdef USE_SSL
   ssize_t nread;