Switch to new API - close #8

The new API is more C-like and will allow consistency across all future
supported language targets.

spec/test_pattern.d

@@ -9,12 +9,13 @@ int main()
 unittest
 {
     string input = "abcdef";
-    auto parser = new Parser(input);
-    assert(parser.parse() == P_SUCCESS);
+    p_context_t context;
+    p_context_init(&context, input);
+    assert(p_parse(&context) == P_SUCCESS);
     writeln("pass1");
 
     input = "defabcdef";
-    parser = new Parser(input);
-    assert(parser.parse() == P_SUCCESS);
+    p_context_init(&context, input);
+    assert(p_parse(&context) == P_SUCCESS);
     writeln("pass2");
 }