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.

Test/baseResults/spv.specConstant.vert.out

@@ -11,7 +11,7 @@ spv.specConstant.vert
                               Source GLSL 400
                               Name 4  "main"
                               Name 9  "arraySize"
-                              Name 14  "foo(vf4[s4393];"
+                              Name 14  "foo(vf4[s4529];"
                               Name 13  "p"
                               Name 17  "builtin_spec_constant("
                               Name 20  "color"
@@ -102,10 +102,10 @@ spv.specConstant.vert
                               Store 20(color) 46
               48:          10 Load 22(ucol)
                               Store 47(param) 48
-              49:           2 FunctionCall 14(foo(vf4[s4393];) 47(param)
+              49:           2 FunctionCall 14(foo(vf4[s4529];) 47(param)
                               Return
                               FunctionEnd
-14(foo(vf4[s4393];):           2 Function None 12
+14(foo(vf4[s4529];):           2 Function None 12
            13(p):     11(ptr) FunctionParameter
               15:             Label
               54:     24(ptr) AccessChain 53(dupUcol) 23