Remove generated parsers' dependency on the runtime library

Generated parsers no longer export a parser constructor function.
They now export an opaque Language object which can be set on
Documents directly. This way, the logic for constructing parsers
lives entirely in the runtime. The Languages are just structs which
have no load-time dependency on the runtime

src/compiler/generate_code/c_code.cc

@@ -163,7 +163,7 @@ class CCodeGenerator {
   }
 
   void parser_export() {
-    line("EXPORT_PARSER(ts_parser_" + name + ");");
+    line("EXPORT_LANGUAGE(ts_language_" + name + ");");
     line();
   }