Change the confusing two variables for the expect 100 continue stuff into

a single state variable to make the code easier to follow and understand.

lib/urldata.h

@@ -672,6 +672,14 @@ typedef CURLcode (*Curl_do_more_func)(struct connectdata *);
 typedef CURLcode (*Curl_done_func)(struct connectdata *, CURLcode, bool);
 
 
+enum expect100 {
+  EXP100_SEND_DATA,           /* enough waiting, just send the body now */
+  EXP100_AWAITING_CONTINUE,   /* waiting for the 100 Continue header */
+  EXP100_SENDING_REQUEST,     /* still sending the request but will wait for
+                                 the 100 header once done with the request */
+  EXP100_FAILED               /* used on 417 Expectation Failed */
+};
+
 /*
  * Request specific data in the easy handle (SessionHandle).  Previously,
  * these members were on the connectdata struct but since a conn struct may
@@ -721,12 +729,8 @@ struct SingleRequest {
   int httpcode;                 /* error code from the 'HTTP/1.? XXX' line */
   int httpversion;              /* the HTTP version*10 */
   struct timeval start100;      /* time stamp to wait for the 100 code from */
-  bool write_after_100_header;  /* TRUE = we enable the write after we
-                                   received a 100-continue/timeout or
-                                   FALSE = directly */
-  bool wait100_after_headers;   /* TRUE = after the request-headers have been
-                                   sent off properly, we go into the wait100
-                                   state, FALSE = don't */
+  enum expect100 exp100;        /* expect 100 continue state */
+
   int content_encoding;         /* What content encoding. sec 3.5, RFC2616. */
 
 #define IDENTITY 0              /* No encoding */