SPV: Turn on atomic-storage functionality for SPIR-V.

This is used by OpenGL, but not Vulkan.
Includes:
 - atomicCounter, atomicIncrement, atomicCounterDecrement
 - atomic_uint layout-offset checking
 - AtomicStorage capability
diff --git a/SPIRV/GlslangToSpv.cpp b/SPIRV/GlslangToSpv.cpp
index de87763..e949547 100755
--- a/SPIRV/GlslangToSpv.cpp
+++ b/SPIRV/GlslangToSpv.cpp
@@ -1832,7 +1832,7 @@
         spvType = builder.makeUintType(64);
         break;
     case glslang::EbtAtomicUint:
-        logger->tbdFunctionality("Is atomic_uint an opaque handle in the uniform storage class, or an addresses in the atomic storage class?");
+        builder.addCapability(spv::CapabilityAtomicStorage);
         spvType = builder.makeUintType(32);
         break;
     case glslang::EbtSampler: