[spirv-reader] First GLSL.std.450 instructions

This supports the extended instructions used by the compute_boids
example.

Bug: tint:3
Change-Id: I364c343217139e489377dd2a9330058114023caa
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/23126
Reviewed-by: dan sinclair <dsinclair@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 4009366..9dbeb92 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -646,6 +646,7 @@
     "src/reader/spirv/function_cfg_test.cc",
     "src/reader/spirv/function_conversion_test.cc",
     "src/reader/spirv/function_decl_test.cc",
+    "src/reader/spirv/function_glsl_std_450_test.cc",
     "src/reader/spirv/function_logical_test.cc",
     "src/reader/spirv/function_memory_test.cc",
     "src/reader/spirv/function_var_test.cc",