Add benchmarks for statement cache.

benches/lib.rs

@@ -0,0 +1,23 @@
+#![feature(test)]
+extern crate test;
+
+extern crate rusqlite;
+
+use rusqlite::Connection;
+use rusqlite::cache::StatementCache;
+use test::Bencher;
+
+#[bench]
+fn bench_no_cache(b: &mut Bencher) {
+    let db = Connection::open_in_memory().unwrap();
+    let sql = "SELECT 1, 'test', 3.14 UNION SELECT 2, 'exp', 2.71";
+    b.iter(|| db.prepare(sql).unwrap());
+}
+
+#[bench]
+fn bench_cache(b: &mut Bencher) {
+    let db = Connection::open_in_memory().unwrap();
+    let cache = StatementCache::new(&db, 15);
+    let sql = "SELECT 1, 'test', 3.14 UNION SELECT 2, 'exp', 2.71";
+    b.iter(|| cache.get(sql).unwrap());
+}