Add mg_http_send_redirect and make examples use it

PUBLISHED_FROM=f45e06aeba1c00212078d539b6f74cb8bd054326

docs/c-api/http_server.h/intro.md

@@ -16,6 +16,7 @@ items:
   - { name: mg_send_http_chunk.md }
   - { name: mg_printf_http_chunk.md }
   - { name: mg_send_response_line.md }
+  - { name: mg_http_send_redirect.md }
   - { name: mg_send_head.md }
   - { name: mg_printf_html_escape.md }
   - { name: mg_fu_fname_fn.md }

docs/c-api/http_server.h/mg_http_send_redirect.md

@@ -0,0 +1,24 @@
+---
+title: "mg_http_send_redirect()"
+decl_name: "mg_http_send_redirect"
+symbol_kind: "func"
+signature: |
+  void mg_http_send_redirect(struct mg_connection *nc, int status_code,
+                             const struct mg_str location,
+                             const struct mg_str extra_headers);
+---
+
+Sends a redirect response.
+`status_code` should be either 301 or 302 and `location` point to the
+new location.
+If `extra_headers` is not empty, then `extra_headers` are also sent
+after the reponse line. `extra_headers` must NOT end end with new line.
+Example:
+
+     mg_send_response_line(nc, 200, "Access-Control-Allow-Origin: *");
+
+Will result in:
+
+     HTTP/1.1 200 OK\r\n
+     Access-Control-Allow-Origin: *\r\n 
+

docs/c-api/http_server.h/mg_send_response_line.md

@@ -3,7 +3,7 @@ title: "mg_send_response_line()"
 decl_name: "mg_send_response_line"
 symbol_kind: "func"
 signature: |
-  void mg_send_response_line(struct mg_connection *c, int status_code,
+  void mg_send_response_line(struct mg_connection *nc, int status_code,
                              const char *extra_headers);
 ---