Change pfenv_print_int to take machine_uint_t rather than unsinged in

With this change, the following works:

>>> print('%#x' % 0x1234567890abcdef)
0x1234567890abcdef

py/pfenv.c

@@ -79,10 +79,10 @@ int pfenv_print_strn(const pfenv_t *pfenv, const char *str, unsigned int len, in
 // We can use 16 characters for 32-bit and 32 characters for 64-bit
 #define INT_BUF_SIZE (sizeof(machine_int_t) * 4)
 
-int pfenv_print_int(const pfenv_t *pfenv, unsigned int x, int sgn, int base, int base_char, int flags, char fill, int width) {
+int pfenv_print_int(const pfenv_t *pfenv, machine_uint_t x, int sgn, int base, int base_char, int flags, char fill, int width) {
     char sign = 0;
     if (sgn) {
-        if ((int)x < 0) {
+        if ((machine_int_t)x < 0) {
             sign = '-';
             x = -x;
         } else if (flags & PF_FLAG_SHOW_SIGN) {

py/pfenv.h

@@ -17,7 +17,7 @@ typedef struct _pfenv_t {
 void pfenv_vstr_add_strn(void *data, const char *str, unsigned int len);
 
 int pfenv_print_strn(const pfenv_t *pfenv, const char *str, unsigned int len, int flags, char fill, int width);
-int pfenv_print_int(const pfenv_t *pfenv, unsigned int x, int sgn, int base, int base_char, int flags, char fill, int width);
+int pfenv_print_int(const pfenv_t *pfenv, machine_uint_t x, int sgn, int base, int base_char, int flags, char fill, int width);
 #if MICROPY_ENABLE_FLOAT
 int pfenv_print_float(const pfenv_t *pfenv, mp_float_t f, char fmt, int flags, char fill, int width, int prec);
 #endif