Add defer delete for encoded strings across all test procedures to ensure
proper cleanup and prevent memory leaks. This completes the memory
management improvements started in 591dd876.
Add test case to verify custom alphabet support. The test uses a
decimal-uppercase alphabet (0-9, A-V) to test both encoding and decoding
with custom tables, including validation. This ensures the encode and
decode functions work correctly with custom encoding tables and
validation functions as documented.
Add test_base32_roundtrip() to verify the encode->decode roundtrip
preserves data integrity. This test helps ensure our base32 implementation
correctly handles the full encode->decode cycle without data loss or
corruption.
Zoltán Kéri