F2FS atomic writes. (#66)

https://sqlite.org/cgi/src/technote/714f6cbbf7

tests/testdata/f2fs.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd -P -- "$(dirname -- "$0")"
+ROOT=../../
+
+if mountpoint -q f2fs/; then
+  sudo umount f2fs/
+fi
+
+mkdir -p f2fs/
+gunzip -c f2fs.img.gz > f2fs.img
+sudo mount -nv -o loop f2fs.img f2fs/
+mkdir -p f2fs/tmp/
+
+go test -c "$ROOT/tests" -coverpkg github.com/ncruces/go-sqlite3/...
+TMPDIR=f2fs/tmp/ ./tests.test -test.v -test.short -test.coverprofile cover.out
+go tool cover -html cover.out
+
+sudo umount f2fs/
+rm -r f2fs/ f2fs.img cover.out *.test