Adds syntax tests, documentation and changelog entry.

Refines comment for array utility function.

test/libsolidity/syntaxTests/array/no_array_pop.sol

@@ -0,0 +1,8 @@
+contract C {
+    uint data;
+    function test() public {
+      data.pop();
+    }
+}
+// ----
+// TypeError: (63-71): Member "pop" not found or not visible after argument-dependent lookup in uint256