security/libsodium: Update to 1.0.22

• PORTVERSION --> DISTVERSION
• Add GitHub as primary MASTER_SITES and upstream's download site as fallback
• Add OPTIMIZED_CFLAGS option (default on)

Changelog:
https://github.com/jedisct1/libsodium/releases/tag/1.0.22-RELEASE

Reference:
https://github.com/jedisct1/libsodium/blob/master/configure.ac#L219

PR: 294415
Approved by: maintainer timeout, 1+ month