Cleanup built-ins, and fix some compiler warnings/errors.
diff --git a/py/mpconfig.h b/py/mpconfig.h
index ada4aa2..5d8c576 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -91,7 +91,7 @@
#define BITS_PER_BYTE (8)
#define BITS_PER_WORD (BITS_PER_BYTE * BYTES_PER_WORD)
// machine_int_t value with most significant bit set
-#define WORD_MSBIT_HIGH (1 << (BYTES_PER_WORD * 8 - 1))
+#define WORD_MSBIT_HIGH (((machine_uint_t)1) << (BYTES_PER_WORD * 8 - 1))
// printf format spec to use for machine_int_t and friends
#ifndef INT_FMT