Fail in a controlled way for asm_thumb use. (#82)

Closes #81

src/demo.html

@@ -88,6 +88,7 @@ <h1>MicroPython-micro:bit simulator example embedding</h1>
               <option value="compass">Compass</option>
               <option value="data_logging">Data logging</option>
               <option value="display">Display</option>
+              <option value="inline_assembler">Inline assembler</option>
               <option value="microphone">Microphone</option>
               <option value="music">Music</option>
               <option value="pin_logo">Pin logo</option>

src/examples/inline_assembler.py

@@ -0,0 +1,12 @@
+from microbit import *
+
+# Unsupported in the simulator
+@micropython.asm_thumb
+def asm_add(r0, r1):
+    add(r0, r0, r1)
+
+while True:
+    if button_a.was_pressed():
+        print(1 + 2)
+    elif button_b.was_pressed():
+        print(asm_add(1, 2))

src/mpconfigport.h

@@ -162,4 +162,7 @@ extern uint32_t rng_generate_random_word(void);
 #define MICROPY_MACHINE_MEM_GET_READ_ADDR machine_mem_get_read_addr
 #define MICROPY_MACHINE_MEM_GET_WRITE_ADDR machine_mem_get_write_addr
 
+#define MICROPY_MAKE_POINTER_CALLABLE(p) \
+    ((mp_raise_NotImplementedError(MP_ERROR_TEXT("simulator limitation: asm_thumb code"))), p)
+
 #endif