stm32,esp8266,cc3200: Use MICROPY_GC_STACK_ENTRY_TYPE to save some RAM.

ports/cc3200/mpconfigport.h

@@ -34,6 +34,7 @@
 
 // options to control how MicroPython is built
 
+#define MICROPY_GC_STACK_ENTRY_TYPE                 uint16_t
 #define MICROPY_ALLOC_PATH_MAX                      (128)
 #define MICROPY_PERSISTENT_CODE_LOAD                (1)
 #define MICROPY_EMIT_THUMB                          (0)

ports/esp8266/mpconfigport.h

@@ -3,6 +3,7 @@
 // options to control how MicroPython is built
 
 #define MICROPY_OBJ_REPR            (MICROPY_OBJ_REPR_C)
+#define MICROPY_GC_STACK_ENTRY_TYPE uint16_t
 #define MICROPY_ALLOC_PATH_MAX      (128)
 #define MICROPY_ALLOC_LEXER_INDENT_INIT (8)
 #define MICROPY_ALLOC_PARSE_RULE_INIT   (48)

ports/stm32/mpconfigport.h

@@ -32,6 +32,13 @@
 #include "mpconfigboard_common.h"
 
 // memory allocation policies
+#ifndef MICROPY_GC_STACK_ENTRY_TYPE
+#if MICROPY_HW_SDRAM_SIZE
+#define MICROPY_GC_STACK_ENTRY_TYPE uint32_t
+#else
+#define MICROPY_GC_STACK_ENTRY_TYPE uint16_t
+#endif
+#endif
 #define MICROPY_ALLOC_PATH_MAX      (128)
 
 // emitters