Update to CRoaring v4.2.1 for #21

[wti]

Update to CRoaring release v4.2.1 for #21

• Aggregated .c and .h files copied from release (first commit)
• Migrated .c off two deprecated API (see below)
• Minor test additions to improve coverage and minimize or bracket print output
• README updated to remove unsupported code (now manually verified)

re: Swift interface:

• Swift 4 is not really supported any more.
• The Swift interface includes inlined functions which don't appear in coverage reports, but tests hit all others. (Coverage of CRoaring is marginal but not at issue here.)

re: CRoaring

• Fixing the two deprecated API's creates a delta with the release code. Let me know if you want instead to leave those as-is.
• There are ~40 warnings about implicit casts. I started to address some in a separate branch, but I stopped because I'm not the one to validate their correctness and deltas are unwelcome.

[lemire]

Running tests.

[wti]

test-macOS.yml is passing, but test-linux.yml has header conflicts.

[wti]

Converted PR to DRAFT. I'll stop investigating for now.

• macOS CI is working
• Linux CI fails to build SwiftRoaring's CRoaring module, even on ubuntu-latest (where CRoaring project CI passes).
• It builds/tests fine on my local stock Ubuntu 24.04 with Swift 6.0.3.
• Unclear if the issue is extrinsic library/build configuration/setup or true problems with amalgamated intrinsics header inclusion in this context.

Let me know if instead you'd like to merge and possibly release, deferring CI fixes.

Sorry for the noise+hassle of an incomplete PR.

[lemire]

I think we ought to figure out the issue prior to merging.

Do you understand the error message? Something to do with intrinsics... ?