Merge branch 'update-glslang' into 'vulkan-cts-1.0'

Update glslang to latest revision



See merge request !448
diff --git a/external/fetch_sources.py b/external/fetch_sources.py
index bcf75c4..efa530d 100644
--- a/external/fetch_sources.py
+++ b/external/fetch_sources.py
@@ -174,7 +174,7 @@
 		"spirv-tools"),
 	GitRepo(
 		"https://github.com/KhronosGroup/glslang.git",
-		"6c292d3ba78533fed7b5ec46bb93b53419cf6535",
+		"5184353326ae52d63a1d7c7fccd66269aab768f7",
 		"glslang"),
 ]