some tests

test/test_custom_hash.c3

@@ -0,0 +1,14 @@
+import std::collections::map;
+
+def Codepoint = uint;
+fn uint Codepoint.hash(Codepoint code) => code < 128 ? code : ((uint)code).hash();
+def CodeMap = map::HashMap(<Codepoint, Codepoint>);
+
+
+fn int main()
+{
+    CodeMap m;
+    m.new_init();
+    m.free();
+    return 0;
+}