[SPIR-V] Update glslang

WIP new vertex fetching

third_party/glslang-spirv/Include/revision.template

@@ -0,0 +1,13 @@
+// The file revision.h should be updated to the latest version, somehow, on
+// check-in, if glslang has changed.
+//
+// revision.template is the source for revision.h when using SubWCRev as the
+// method of updating revision.h.  You don't have to do it this way, the
+// requirement is only that revision.h gets updated.
+//
+// revision.h is under source control so that not all consumers of glslang
+// source have to figure out how to create revision.h just to get a build
+// going.  However, if it is not updated, it can be a version behind.
+
+#define GLSLANG_REVISION "$WCREV$"
+#define GLSLANG_DATE     "$WCDATE$"