Update glslang, SPIR-V Tools, headers to 1.6

Switched to internal Khronos repo until 1.6 is released.

Components: Framework
Change-Id: Idf3ea328a2ce03b5f12eb4c44fc1ba2e53ee396f
diff --git a/external/fetch_sources.py b/external/fetch_sources.py
index f9b91c3..fb76870 100644
--- a/external/fetch_sources.py
+++ b/external/fetch_sources.py
@@ -315,20 +315,20 @@
 		"e7b5f0aa5b1b0eadc63a1c624c0ca7f5af133aa857d6a4271b0ef3d0bdb6868e",
 		"renderdoc"),
 	GitRepo(
-		"https://github.com/KhronosGroup/SPIRV-Tools.git",
-		None,
-		"ee30773650eca50b1cd3c913babcc2b50d7b91fd",
+		"https://gitlab.khronos.org/spirv/spirv-tools.git",
+		"git@gitlab.khronos.org:spirv/spirv-tools.git",
+		"0ed26bdf3889b0a19018d1812c879aeaebc14fb4",
 		"spirv-tools"),
 	GitRepo(
-		"https://github.com/KhronosGroup/glslang.git",
-		None,
-		"9158061398a96033c990e69156bd28c67114544b",
+		"https://gitlab.khronos.org/GLSL/glslang.git",
+		"git@gitlab.khronos.org:GLSL/glslang.git",
+		"0d80fdd4d327ee38cabdcc2978b7b61da2359a30",
 		"glslang",
 		removeTags = ["master-tot"]),
 	GitRepo(
-		"https://github.com/KhronosGroup/SPIRV-Headers.git",
-		None,
-		"449bc986ba6f4c5e10e32828783f9daef2a77644",
+		"https://gitlab.khronos.org/spirv/SPIRV-Headers.git",
+		"git@gitlab.khronos.org:spirv/SPIRV-Headers.git",
+		"73bf8a239d5e3a7ef37ede266fcf7d1e485f8a66",
 		"spirv-headers"),
 	GitRepo(
 		"https://github.com/google/amber.git",