Emit spirv_internal.hpp include

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@23a28b9

Author: svenvh

llvm-spirv/tools/spirv-tool/gen_spirv.bash

@@ -164,6 +164,7 @@ genFile() {
 
 #include \"SPIRVEnum.h\"
 #include \"spirv.hpp\"
+#include \"spirv_internal.hpp\"
 
 using namespace spv;