Non-Functional: Add postprocess as more robust way to add capabilities

When capabilities are needed for specific SPIR-V instructions, it is
fragile to do so based on GLSL/AST usage; it should be based on actual
instructions they got translated to.

SPIRV/CMakeLists.txt

@@ -3,6 +3,7 @@ set(SOURCES
     InReadableOrder.cpp
     Logger.cpp
     SpvBuilder.cpp
+    SpvPostProcess.cpp
     doc.cpp
     disassemble.cpp)