Sema: better source location for function call args

test/cases/compile_errors/implicitly_increasing_pointer_alignment.zig

@@ -0,0 +1,20 @@
+const Foo = packed struct {
+    a: u8,
+    b: u32,
+};
+
+export fn entry() void {
+    var foo = Foo { .a = 1, .b = 10 };
+    bar(&foo.b);
+}
+
+fn bar(x: *u32) void {
+    x.* += 1;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :8:9: error: expected type '*u32', found '*align(1) u32'
+// :8:9: note: pointer alignment '1' cannot cast into pointer alignment '4'