Add test that rand() produces both even and odd numbers (fails). See #2341.
Migrate to musl v1.0.3 prng functions. Fixes #2341. Bump version to 1.23.1 to have cached libc rebuilt with prng routines.
Improve test_rand to test all produced bits, not just the lowest one.
Merge pull request #2719 from juj/musl_rand

Musl rand