Organizing array tests into more directories.

test/libsolidity/semanticTests/array/pop/array_pop.sol

@@ -0,0 +1,17 @@
+contract c {
+    uint256[] data;
+
+    function test() public returns (uint256 x, uint256 l) {
+        data.push(7);
+        data.push(3);
+        x = data.length;
+        data.pop();
+        x = data.length;
+        data.pop();
+        l = data.length;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// test() -> 1, 0