CodeWriter: Add CodeWriterType.FAST enum value

Designed to emit .vapi files before the resolution stage has run.

Includes 'using' in the output so that the resolver can figure it out
later.

Also includes the values of constants and enums so that headers are not
required.

vala/valacodewriter.vala

@@ -89,6 +89,12 @@ public class Vala.CodeWriter : CodeVisitor {
 		stream = null;
 	}
 
+	public override void visit_using_directive (UsingDirective ns) {
+		if (type == CodeWriterType.FAST) {
+			write_string ("using %s;\n".printf (ns.namespace_symbol.name));
+		}
+	}
+
 	public override void visit_namespace (Namespace ns) {
 		if (ns.external_package) {
 			return;
@@ -211,7 +217,7 @@ public class Vala.CodeWriter : CodeVisitor {
 
 		write_string ("[CCode (");
 
-		if (cl.is_reference_counting ()) {
+		if (cl.is_reference_counting () && type != CodeWriterType.FAST) {
 			if (cl.base_class == null || cl.base_class.get_ref_function () == null || cl.base_class.get_ref_function () != cl.get_ref_function ()) {
 				write_string ("ref_function = \"%s\", ".printf (cl.get_ref_function ()));
 				if (cl.ref_function_void) {
@@ -555,6 +561,11 @@ public class Vala.CodeWriter : CodeVisitor {
 			}
 			write_indent ();
 			write_identifier (ev.name);
+
+			if (type == CodeWriterType.FAST && ev.value != null) {
+				write_string(" = ");
+				ev.value.accept (this);
+			}
 		}
 
 		if (!first) {
@@ -653,6 +664,10 @@ public class Vala.CodeWriter : CodeVisitor {
 
 		write_string (" ");
 		write_identifier (c.name);
+		if (type == CodeWriterType.FAST && c.value != null) {
+			write_string(" = ");
+			c.value.accept (this);
+		}
 		write_string (";");
 		write_newline ();
 	}
@@ -1889,6 +1904,7 @@ public class Vala.CodeWriter : CodeVisitor {
 			       sym.access == SymbolAccessibility.PROTECTED;
 
 		case CodeWriterType.INTERNAL:
+		case CodeWriterType.FAST:
 			return sym.access == SymbolAccessibility.INTERNAL ||
 			       sym.access == SymbolAccessibility.PUBLIC ||
 			       sym.access == SymbolAccessibility.PROTECTED;
@@ -1951,5 +1967,6 @@ public class Vala.CodeWriter : CodeVisitor {
 public enum CodeWriterType {
 	EXTERNAL,
 	INTERNAL,
+	FAST,
 	DUMP
 }