py: Add mp_raise_msg_varg helper and use it where appropriate.

This commit adds mp_raise_msg_varg(type, fmt, ...) as a helper for
nlr_raise(mp_obj_new_exception_msg_varg(type, fmt, ...)).  It makes the
C-level API for raising exceptions more consistent, and reduces code size
on most ports:

   bare-arm:   +28 +0.042%
minimal x86:  +100 +0.067%
   unix x64:   -56 -0.011%
unix nanbox:  -300 -0.068%
      stm32:  -204 -0.054% PYBV10
     cc3200:    +0 +0.000%
    esp8266:   -64 -0.010% GENERIC
      esp32:  -104 -0.007% GENERIC
        nrf:  -136 -0.094% pca10040
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS

1 files changed, 3 insertions, 0 deletions

diff --git a/py/obj.h b/py/obj.h
index e3eb85e13..fece5e73d 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -712,6 +712,9 @@ mp_obj_t mp_obj_new_exception_arg1(const mp_obj_type_t *exc_type, mp_obj_t arg);
 mp_obj_t mp_obj_new_exception_args(const mp_obj_type_t *exc_type, size_t n_args, const mp_obj_t *args);
 mp_obj_t mp_obj_new_exception_msg(const mp_obj_type_t *exc_type, const char *msg);
 mp_obj_t mp_obj_new_exception_msg_varg(const mp_obj_type_t *exc_type, const char *fmt, ...); // counts args by number of % symbols in fmt, excluding %%; can only handle void* sizes (ie no float/double!)
+#ifdef va_start
+mp_obj_t mp_obj_new_exception_msg_varg2(const mp_obj_type_t *exc_type, const char *fmt, va_list arg); // counts args by number of % symbols in fmt, excluding %%; can only handle void* sizes (ie no float/double!)
+#endif
 mp_obj_t mp_obj_new_fun_bc(mp_obj_t def_args, mp_obj_t def_kw_args, const byte *code, const mp_uint_t *const_table);
 mp_obj_t mp_obj_new_fun_native(mp_obj_t def_args_in, mp_obj_t def_kw_args, const void *fun_data, const mp_uint_t *const_table);
 mp_obj_t mp_obj_new_fun_asm(size_t n_args, const void *fun_data, mp_uint_t type_sig);