Make most tests an example so we can run them one by one

clippy_tests/examples/assign_ops.rs

@@ -0,0 +1,41 @@
+#![feature(plugin)]
+#![plugin(clippy)]
+
+#[warn(assign_ops)]
+#[allow(unused_assignments)]
+fn main() {
+    let mut i = 1i32;
+    i += 2;
+    i += 2 + 17;
+    i -= 6;
+    i -= 2 - 1;
+    i *= 5;
+    i *= 1+5;
+    i /= 32;
+    i /= 32 | 5;
+    i /= 32 / 5;
+    i %= 42;
+    i >>= i;
+    i <<= 9 + 6 - 7;
+    i += 1 << 5;
+}
+
+#[allow(dead_code, unused_assignments)]
+#[warn(assign_op_pattern)]
+fn bla() {
+    let mut a = 5;
+    a = a + 1;
+    a = 1 + a;
+    a = a - 1;
+    a = a * 99;
+    a = 42 * a;
+    a = a / 2;
+    a = a % 5;
+    a = a & 1;
+    a = 1 - a;
+    a = 5 / a;
+    a = 42 % a;
+    a = 6 << a;
+    let mut s = String::new();
+    s = s + "bla";
+}