NaCl docs: update version information

native_client_sdk/src/doc/reference/pnacl-bitcode-abi.rst

 ==============================
 PNaCl Bitcode Reference Manual
 ==============================
 
 .. contents::
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 Introduction
 ============
 
 This document is a reference manual for the PNaCl bitcode format. It describes
 the bitcode on a *semantic* level; the physical encoding level will be described
 elsewhere. For the purpose of this document, the textual form of LLVM IR is
 used to describe instructions and other bitcode constructs.
 
-Since the PNaCl bitcode is based to a large extent on LLVM IR, many sections
-in this document point to a relevant section of the LLVM language reference
-manual. Only the changes, restrictions and variations specific to PNaCl are
-described---full semantic descriptions are not duplicated from the LLVM
-reference manual.
+Since the PNaCl bitcode is based to a large extent on LLVM IR as of
+version 3.3, many sections in this document point to a relevant section
+of the LLVM language reference manual. Only the changes, restrictions
+and variations specific to PNaCl are described---full semantic
+descriptions are not duplicated from the LLVM reference manual.
 
 High Level Structure
 ====================
 
 A PNaCl portable executable (**pexe** in short) is a single LLVM IR module.
 
 Data Model
 ----------
 
 The data model for PNaCl bitcode is fixed at little-endian ILP32: pointers are
@@ skipping 512 matching lines @@
 
     declare i1 @llvm.nacl.atomic.is.lock.free(i32 <byte_size>, i8* <address>)
 
 The ``llvm.nacl.atomic.is.lock.free`` intrinsic is designed to
 determine at translation time whether atomic operations of a certain
 ``byte_size`` (a compile-time constant), at a particular ``address``,
 are lock-free or not. This reflects the C11 ``atomic_is_lock_free``
 function from header ``<stdatomic.h>`` and the C++11 ``is_lock_free``
 member function in header ``<atomic>``. It can be used through the
 ``__nacl_atomic_is_lock_free`` builtin.