Add parentheses to mute compiler warning

ex:

src/wal.cc:79:270: warning: '&' within '|' [-Wbitwise-op-parentheses]
    return (int32_t) ( ( (((uint64_t)(((aa->seqnum) & ((0x8000000000000000ULL)))^((bb->seqnum) & ((0x8000000000000000ULL))))>>63)-1) & ( (((aa->seqnum)-(bb->seqnum))>>32) | (( ((uint64_t)(aa->seqnum)-(bb->seqnum)) | (~((uint64_t)(aa->seqnum)-(bb->seqnum)) + 1)) >> 63) & 0x1 ) ) | ( (((uint64_t)(((aa->seqnum) & ((0x8000000000000000ULL)))^((bb->seqnum) & ((0x8000000000000000ULL))))>>32) | ((uint64_t)(((aa->seqnum) & ((0x8000000000000000ULL)))^((bb->seqnum) & ((0x8000000000000000ULL))))>>63)) & ( (((bb->seqnum) & ((0x8000000000000000ULL))) >> 32) | 0x1)));
src/wal.cc:79:270: note: place parentheses around the '&' expression to silence this warning
    return (int32_t) ( ( (((uint64_t)(((aa->seqnum) & ((0x8000000000000000ULL)))^((bb->seqnum) & ((0x8000000000000000ULL))))>>63)-1) & ( (((aa->seqnum)-(bb->seqnum))>>32) | (( ((uint64_t)(aa->seqnum)-(bb->seqnum)) | (~((uint64_t)(aa->seqnum)-(bb->seqnum)) + 1)) >> 63) & 0x1 ) ) | ( (((uint64_t)(((aa->seqnum) & ((0x8000000000000000ULL)))^((bb->seqnum) & ((0x8000000000000000ULL))))>>32) | ((uint64_t)(((aa->seqnum) & ((0x8000000000000000ULL)))^((bb->seqnum) & ((0x8000000000000000ULL))))>>63)) & ( (((bb->seqnum) & ((0x8000000000000000ULL))) >> 32) | 0x1)));
                                                                                                                                                                             (                                                                                                    )

Change-Id: Idf2769b4f67149df6d7f66212f15b2fca8b8144f