Fix UB on some bit array operations

C promotes arithmetic to int regardless of what type the values are
eventually going to fit into. So if int is 32 bits, and leftover is
32 or more, UB. This was causing operations to read from the
undefined (actually zero) part of the word.

Author: Bike

src/core/array_bit.cc

@@ -134,7 +134,7 @@ CL_DEFUN SimpleBitVector_sp core__sbv_bit_not(SimpleBitVector_sp vec, SimpleBitV
     }                                                                                                                              \
     i = nwords;                                                                                                                    \
     if (leftover != 0) {                                                                                                           \
-      bit_array_word mask = ((1 << leftover) - 1) << (BIT_ARRAY_WORD_BITS - leftover);                                             \
+      bit_array_word mask = (((bit_array_word)1 << leftover) - 1) << (BIT_ARRAY_WORD_BITS - leftover);                             \
       word = bytes[i] & mask;                                                                                                      \
       statement                                                                                                                    \
     }                                                                                                                              \