Add file missed in previous commit.

From-SVN: r168684

libgo/runtime/go-cgo.c

+/* go-cgo.c -- SWIG support routines for libgo.
+
+   Copyright 2011 The Go Authors. All rights reserved.
+   Use of this source code is governed by a BSD-style
+   license that can be found in the LICENSE file.  */
+
+#include "go-alloc.h"
+#include "interface.h"
+#include "go-panic.h"
+#include "go-string.h"
+
+/* These are routines used by SWIG.  The gc runtime library provides
+   the same routines under the same name, though in that case the code
+   is required to import runtime/cgo.  */
+
+void *
+_cgo_allocate (size_t n)
+{
+  return __go_alloc (n);
+}
+
+extern const struct __go_type_descriptor string_type_descriptor
+  asm ("__go_tdn_string");
+
+void
+_cgo_panic (const char *p)
+{
+  int len;
+  unsigned char *data;
+  struct __go_string *ps;
+  struct __go_empty_interface e;
+
+  len = __builtin_strlen (p);
+  data = __go_alloc (len);
+  __builtin_memcpy (data, p, len);
+  ps = __go_alloc (sizeof *ps);
+  ps->__data = data;
+  ps->__length = len;
+  e.__type_descriptor = &string_type_descriptor;
+  e.__object = ps;
+  __go_panic (e);
+}