Remove uses of 'in' on extern(C) functions

It is forbidden by DMD master.

etc/c/curl.d

@@ -1372,9 +1372,9 @@ alias curl_TimeCond = int;
 /** curl_strequal() and curl_strnequal() are subject for removal in a future
    libcurl, see lib/README.curlx for details */
 extern (C) {
-int  curl_strequal(in const(char) *s1, in const(char) *s2);
+int  curl_strequal(scope const(char) *s1, scope const(char) *s2);
 /// ditto
-int  curl_strnequal(in const(char) *s1, in const(char) *s2, size_t n);
+int  curl_strnequal(scope const(char) *s1, scope const(char) *s2, size_t n);
 }
 enum CurlForm {
     nothing, /********** the first one is unused ************/
@@ -1464,7 +1464,7 @@ CURLFORMcode  curl_formadd(curl_httppost **httppost, curl_httppost **last_post,.
  * Should return the buffer length passed to it as the argument "len" on
  *   success.
  */
-alias curl_formget_callback = size_t function(void *arg, in const(char) *buf, size_t len);
+alias curl_formget_callback = size_t function(void *arg, const(char) *buf, size_t len);
 
 /**
  * Name: curl_formget()
@@ -1514,10 +1514,10 @@ char * curl_version();
  * %XX versions). This function returns a new allocated string or NULL if an
  * error occurred.
  */
-char * curl_easy_escape(CURL *handle, in const(char) *string, int length);
+char * curl_easy_escape(CURL *handle, scope const(char) *string, int length);
 
 /** the previous version: */
-char * curl_escape(in const(char) *string, int length);
+char * curl_escape(scope const(char) *string, int length);
 
 
 /**
@@ -1531,10 +1531,10 @@ char * curl_escape(in const(char) *string, int length);
  * Conversion Note: On non-ASCII platforms the ASCII %XX codes are
  * converted into the host encoding.
  */
-char * curl_easy_unescape(CURL *handle, in const(char) *string, int length, int *outlength);
+char * curl_easy_unescape(CURL *handle, scope const(char) *string, int length, int *outlength);
 
 /** the previous version */
-char * curl_unescape(in const(char) *string, int length);
+char * curl_unescape(scope const(char) *string, int length);
 
 /**
  * Name: curl_free()
@@ -1608,7 +1608,7 @@ struct curl_slist
  * Appends a string to a linked list. If no list exists, it will be created
  * first. Returns the new list, after appending.
  */
-curl_slist * curl_slist_append(curl_slist *, in const(char) *);
+curl_slist * curl_slist_append(curl_slist *, const(char) *);
 
 /**
  * Name: curl_slist_free_all()