Proper support for registering builtin modules in ROM.

Comes with some refactoring of code and renaming of files.  All modules
are now named mod*.[ch].

py/modmicropython.c

@@ -0,0 +1,50 @@
+#include "misc.h"
+#include "mpconfig.h"
+#include "qstr.h"
+#include "obj.h"
+#include "map.h"
+#include "builtin.h"
+
+// Various builtins specific to MicroPython runtime,
+// living in micropython module
+
+#if MICROPY_MEM_STATS
+STATIC mp_obj_t mp_micropython_mem_total() {
+    return MP_OBJ_NEW_SMALL_INT((machine_int_t)m_get_total_bytes_allocated());
+}
+
+STATIC mp_obj_t mp_micropython_mem_current() {
+    return MP_OBJ_NEW_SMALL_INT((machine_int_t)m_get_current_bytes_allocated());
+}
+
+STATIC mp_obj_t mp_micropython_mem_peak() {
+    return MP_OBJ_NEW_SMALL_INT((machine_int_t)m_get_peak_bytes_allocated());
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(mp_micropython_mem_total_obj, mp_micropython_mem_total);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(mp_micropython_mem_current_obj, mp_micropython_mem_current);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(mp_micropython_mem_peak_obj, mp_micropython_mem_peak);
+#endif
+
+STATIC const mp_map_elem_t mp_module_micropython_globals_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_micropython) },
+#if MICROPY_MEM_STATS
+    { MP_OBJ_NEW_QSTR(MP_QSTR_mem_total), (mp_obj_t)&mp_micropython_mem_total_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_mem_current), (mp_obj_t)&mp_micropython_mem_current_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_mem_peak), (mp_obj_t)&mp_micropython_mem_peak_obj },
+#endif
+};
+
+STATIC const mp_map_t mp_module_micropython_globals = {
+    .all_keys_are_qstrs = 1,
+    .table_is_fixed_array = 1,
+    .used = sizeof(mp_module_micropython_globals_table) / sizeof(mp_map_elem_t),
+    .alloc = sizeof(mp_module_micropython_globals_table) / sizeof(mp_map_elem_t),
+    .table = (mp_map_elem_t*)mp_module_micropython_globals_table,
+};
+
+const mp_obj_module_t mp_module_micropython = {
+    .base = { &mp_type_module },
+    .name = MP_QSTR_micropython,
+    .globals = (mp_map_t*)&mp_module_micropython_globals,
+};