Updates tinyformat.h to commit c42f/tinyformat@689695c upstream. Including:
https://github.com/c42f/tinyformat/commit/8a2812d8480bfb66923eea0bb5cdda79fe4f17ba
https://github.com/c42f/tinyformat/commit/5d9e05a3479d1b2ec6a4602fd797f0ec26440db2
https://github.com/c42f/tinyformat/commit/48e2e48789907f80a7aec24a3f1d69196b78ed43
@achow101 mentioned that since upgrading to Ubuntu 17.10 (GCC 7), tinyformat had been throwing lots of -Wimplicit-fallthrough warnings. However fallthrough warnings should have been silenced by #10489. cc @theuni.
The upstream commit to fix fallthrough warnings is in this PR https://github.com/c42f/tinyformat/pull/39.
The last time tinyformat.h was updated in this repo was in #8274.