Rework ES2015 module system and add missing features. (#2792)

Co-authored-by: Dániel Bátyai <dbatyai@inf.u-szeged.hu>
JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu
JerryScript-DCO-1.0-Signed-off-by: Daniel Vince vinced@inf.u-szeged.hu

docs/05.PORT-API.md

@@ -85,7 +85,8 @@ void jerry_port_print_char (char c);
 
 ### ES2015 Module system helper functions
 
-The import statement requires two specific functions for opening and closing files (the modules) port specific.
+The module system requires two specific functions for opening and closing files.
+It also requires a platform specific way of normalizing file paths.
 
 ```c
 /**
@@ -108,6 +109,21 @@ jerry_port_release_source (uint8_t *buffer_p) /**< buffer to free */
 {
   free (buffer_p);
 } /* jerry_port_release_source */
+
+/**
+ * Normalize a file path
+ *
+ * @return length of the path written to the output buffer
+ */
+size_t
+jerry_port_normalize_path (const char *in_path_p, /**< input file path */
+                           char *out_buf_p,       /**< output buffer */
+                           size_t out_buf_size)   /**< size of output buffer */
+{
+  // normalize in_path_p by expanding relative paths etc.
+  // write to out_buf_p the normalized path
+  // return length of written path
+} /* jerry_port_normalize_path */
 ```
 
 ## Date