Fix Windows ARM/ARM64 __builtin_popcountl to handle u64

[anonymou0719]

Summary

This PR ports a small bug fix from vlasky/sqlite-vec into asg017/sqlite-vec.

The ARM/ARM64 fallback implementation was taking an unsigned int instead of u64, which truncated the upper 32 bits when called from distance_hamming_u64. This change fixes the type to make the ARM/ARM64 path consistent with the x86 32-bit implementation.

commit

• URL: http://github.com/vlasky/sqlite-vec/commit/2bd13b2140bb047ca30d0e65160f45cfd247b12d
• What it does: Fixes the ARM/ARM64 fallback argument type to use u64 so distance_hamming_u64 works correctly without losing the upper 32 bits.

Why it fits this repo’s guidelines/policies

• Correctness fix: Prevents truncation on ARM/ARM64 when computing Hamming distance with 64-bit inputs.
• Minimal and review-friendly: Limited to a small change in sqlite-vec.c, no refactors or unrelated edits.
• Compatibility-preserving: No API changes; behavior is simply corrected to match intended 64-bit semantics.

Notes (if any adaptations): Ported cleanly from vlasky/sqlite-vec with no functional deviations intended.

Why it’s useful here

• Benefit: Bug fix for Hamming distance calculations on ARM/ARM64.
• Impact: Ensures correct results for 64-bit distance computations across architectures and avoids silent incorrect behavior on non-x86 platforms.

Testing

• Existing tests: ✅ Verified locally; build/tests pass
• CI link (if any): N/A
• Extra tests (if any): None