INTEL_shader_integer_functions2: Add compiler front-end support

The changes to glslang/glslang/MachineIndependent/ParseHelper.cpp exist
purely to prevent even more instances of "warning: enumeration value
‘EOp...’ not handled in switch"

v2: Remove 8-bit types.  Overzealous copy-and-paste led to adding
support for a bunch of types that the extension doesn't actually enable.

v3: Update expected test results file.  Just changing an expected
results file to make a test pass seems sketchy to me, but I'm not sure
what else to do.

v4: Add missing entry for EOpAbsDifference in
TOutputTraverser::visitBinary.  Noticed by JohnK.

glslang/Include/intermediate.h

@@ -899,6 +899,15 @@ enum TOperator {
     EOpFindLSB,
     EOpFindMSB,
 
+    EOpCountLeadingZeros,
+    EOpCountTrailingZeros,
+    EOpAbsDifference,
+    EOpAddSaturate,
+    EOpSubSaturate,
+    EOpAverage,
+    EOpAverageRounded,
+    EOpMul32x16,
+
     EOpTraceNV,
     EOpReportIntersectionNV,
     EOpIgnoreIntersectionNV,