Add SSI include file=, include virtual=

mongoose.h

@@ -296,6 +296,10 @@ typedef int socklen_t;
 #define MG_ENABLE_FS 1
 #endif
 
+#ifndef MG_ENABLE_SSI
+#define MG_ENABLE_SSI 0
+#endif
+
 #ifndef MG_ENABLE_IPV6
 #define MG_ENABLE_IPV6 0
 #endif
@@ -667,8 +671,8 @@ struct mg_http_message {
 
 // Parameter for mg_http_serve_dir()
 struct mg_http_serve_opts {
-  const char *root_dir;
-  const char *ssi_pattern;
+  const char *root_dir;     // Web root directory, must be non-NULL
+  const char *ssi_pattern;  // SSI filename pattern, e.g. #.shtml
 };
 
 int mg_http_parse(const char *s, size_t len, struct mg_http_message *);
@@ -680,7 +684,7 @@ struct mg_connection *mg_http_listen(struct mg_mgr *, const char *url,
 struct mg_connection *mg_http_connect(struct mg_mgr *, const char *url,
                                       mg_event_handler_t fn, void *fn_data);
 void mg_http_serve_dir(struct mg_connection *, struct mg_http_message *hm,
-                       const struct mg_http_serve_opts *);
+                       struct mg_http_serve_opts *);
 void mg_http_serve_file(struct mg_connection *, struct mg_http_message *,
                         const char *, const char *mime);
 void mg_http_reply(struct mg_connection *, int status_code, const char *headers,
@@ -696,6 +700,10 @@ int mg_http_upload(struct mg_connection *, struct mg_http_message *hm,
 void mg_http_bauth(struct mg_connection *, const char *user, const char *pass);
 
 
+void mg_http_serve_ssi(struct mg_connection *c, const char *root,
+                       const char *fullpath);
+
+
 
 struct mg_tls_opts {
   const char *ca;        // CA certificate file. For both listeners and clients