Add gdbinit to tools/ directory.

tools/gdbinit

Index: tools/gdbinit
diff --git a/tools/gdbinit b/tools/gdbinit
new file mode 100644
index 0000000000000000000000000000000000000000..0c99ae1e013e53ca5f58af1aba304610ff37e117
--- /dev/null
+++ b/tools/gdbinit
@@ -0,0 +1,33 @@
+# Copyright 2014 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Print HeapObjects.
+define job
+print ((v8::internal::HeapObject*)($arg0))->Print()
+end
+document job
+Print a v8 JavaScript object
+Usage: job tagged_ptr
+end
+
+# Print Code objects containing given PC.
+define jco
+job (v8::internal::Isolate::Current()->FindCodeObject((v8::internal::Address)$arg0))
+end
+document jco
+Print a v8 Code object from an internal code address
+Usage: jco pc
+end
+
+# Print JavaScript stack trace.
+define jst 
+print v8::internal::Isolate::Current()->PrintStack(stdout)
+end
+document jst
+Print the current JavaScript stack trace
+Usage: jst
+end
+
+set disassembly-flavor intel
+set disable-randomization off