Removing empty errors tests - tests that are valid C/C++ code

Examples/test-suite/errors/c_varargs.i

@@ -1,3 +0,0 @@
-%module xxx
-
-int foo(int x, ...);

Examples/test-suite/errors/cpp_overload.i

@@ -1,15 +0,0 @@
-%module xxx
-int foo(int x);
-int foo(double x);
-
-class Foo {
-public:
-    int bar(int);
-    int bar(double);
-};
-
-class Spam {
-public:
-    Spam();
-    Spam(int);
-};

Examples/test-suite/errors/cpp_private_defvalue.i

@@ -1,7 +0,0 @@
-%module xxx
-
-class foo {
-static const int BAR = 42;
-public:
-   int blah(int x = BAR);
-};