Rename jerry-port.h to jerryscript-port.h (#1762)

All public headers should follow the pattern `jerryscript[-*].h`.
The `jerry-api.h` to `jerryscript.h` renaming has already happened
a while ago, now it's time for the port API header to follow.

This patch
* renames the public header file,
* updates all includes to use the new file name (in `jerry-main`,
  in all the targets, and in the docs), and
* keeps `jerry-port.h` as a deprecated forwarding header to leave
  some time for external users to follow up with this change.

As a related change, the header of the default port implementation
is also changed to `jerryscript-port-default.h`.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

targets/nuttx-stm32f4/jerry_main.c

@@ -19,7 +19,7 @@
 #include <setjmp.h>
 
 #include "jerryscript.h"
-#include "jerry-port.h"
+#include "jerryscript-port.h"
 #include "jmem.h"
 
 /**