SPV: Make OpEntryPoint I/O list include all static uses.

Before, it was only including explicit interface, sufficient for IO-Block-declared
oriented interface, but not sufficient for all modes GLSL might be used with
SPIR-V.

Two things are accomplished now:
1) each id will appear exactly once
2) the OpEntryPoint list will union static use with declarations

Test/baseResults/spv.400.frag.out

@@ -12,7 +12,7 @@ Linked fragment stage:
                               Capability Shader
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
-                              EntryPoint Fragment 4  "main" 50 44 11 96 69 119 56
+                              EntryPoint Fragment 4  "main" 11 44 50 96 56 117 69 119
                               ExecutionMode 4 OriginLowerLeft
                               Source GLSL 400
                               SourceExtension  "GL_ARB_separate_shader_objects"