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.300layoutp.vert.out

@@ -10,7 +10,7 @@ Linked vertex stage:
                               Capability Shader
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
-                              EntryPoint Vertex 4  "main" 53 11 73 9 51 61 81 115 116
+                              EntryPoint Vertex 4  "main" 81 9 73 51 115 11 61 53 116
                               Source ESSL 300
                               Name 4  "main"
                               Name 9  "pos"