fix Issue 313 - [module] Fully qualified names bypass private imports

test/fail_compilation/imports/test313a.d

@@ -0,0 +1,4 @@
+module imports.test313a;
+
+// explicit private no longer needed but added for clarity
+private import std.stdio;

test/fail_compilation/test313.d

@@ -0,0 +1,17 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/test313.d(13): Error: undefined identifier writefln
+fail_compilation/test313.d(16): Error: undefined identifier std
+---
+*/
+import imports.test313a;
+
+void main()
+{
+    // compiler correctly reports "undefined identifier writefln"
+    writefln("foo");
+
+    // works fine! --> correctly reports "undefined identifier std"
+    std.stdio.writefln("foo");
+}