Implement global atomics and a memory barrier in the standard library.

This checkin provides the standard set of atomic operations and a memory barrier in the ispc standard library.  Both signed and unsigned 32- and 64-bit integer types are supported.

docs/ReleaseNotes.txt

@@ -1,9 +1,9 @@
-=== v1.0.3 === (not yet released)
+=== v1.0.3 === (4 July 2011)
 
 ispc now has a bulit-in pre-processor (from LLVM's clang compiler).
-(Thanks to Pete Couperus!)  It is therefore no longer necessary to use
-cl.exe for preprocessing before on Windows; the MSVC proejct files for the
-examples have been updated accordingly.
+(Thanks to Pete Couperus for this patch!)  It is therefore no longer
+necessary to use cl.exe for preprocessing on Windows; the MSVC proejct
+files for the examples have been updated accordingly.
 
 There is another variant of the shuffle() function int the standard
 library: "<type> shuffle(<type> v0, <type> v1, int permute)", where the
@@ -11,8 +11,15 @@ permutation vector indexes over the concatenation of the two vectors
 (e.g. the value 0 corresponds to the first element of v0, the value
 2*programCount-1 corresponds to the last element of v1, etc.)
 
+ispc now supports the usual range of atomic operations (add, subtract, min,
+max, and, or, and xor) as well as atomic swap and atomic compare and
+exchange.  There is also a facility for inserting memory fences.  See the
+"Atomic Operations and Memory Fences" section of the user's guide
+(http://ispc.github.com/ispc.html#atomic-operations-and-memory-fences) for
+more information.
+ 
 There are now both 'signed' and 'unsigned' variants of the standard library
-functions like packed_load_active() that that references to arrays of
+functions like packed_load_active() that take references to arrays of
 signed int32s and unsigned int32s respectively.  (The
 {load_from,store_to}_{int8,int16}() functions have similarly been augmented
 to have both 'signed' and 'unsigned' variants.)