Add tests

Author: Daniel-Cortez

source/compiler/tests/gh_685.meta

@@ -0,0 +1,7 @@
+{
+  'test_type': 'output_check',
+  'errors': """
+gh_685.pwn(1) : error 010: invalid function or declaration
+gh_685.pwn(2) : error 010: invalid function or declaration
+  """
+}

source/compiler/tests/gh_685.pwn

@@ -0,0 +1,4 @@
+native Tag:[1]operator +(Tag:a, Tag:b) = 0; // error 010: invalid function or declaration
+forward Tag:[1]operator -(Tag:a,Tag:b); // error 010: invalid function or declaration
+
+main () { }