fix(rust): Fix 32-bit build failures (i686, armv7l)

[cfsmp3]

Summary

Fix two build failures on 32-bit architectures reported by Void Linux maintainer.

Fix 1: i686 build failure (#1937)

The code was importing std::arch::x86_64::* even when compiled for 32-bit x86:

#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
use std::arch::x86_64::*;  // ERROR: x86_64 module doesn't exist on i686

Fix: Use separate conditional imports for each architecture.

Fix 2: armv7l build failure (#1938)

The literal 0xcdcdcdcdcdcdcdcd is a 64-bit value that doesn't fit in 32-bit usize:

error: literal out of range for `usize`
   --> src/libccxr_exports/demuxer.rs:269:63
    |
269 |             if buffer_ptr.is_null() || buffer_ptr as usize == 0xcdcdcdcdcdcdcdcd {
    |                                                               ^^^^^^^^^^^^^^^^^^

Fix: Define a platform-appropriate constant (64-bit: 0xcdcdcdcdcdcdcdcd, 32-bit: 0xcdcdcdcd).

Test plan

• Verified cargo check passes on x86_64
• Void Linux maintainer to verify i686 build works
• Void Linux maintainer to verify armv7l build works

Fixes #1937
Fixes #1938

🤖 Generated with Claude Code

[ccextractor-bot]

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 64ce4ac...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	7/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	81/86
Teletext	21/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65...
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b...
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

Check the result page for more info.