Memory: Non-Functional: Rationalize and improve encapsulation of TLS usage.

This will make the next (functional) commit easier to see.

OGLCompilersDLL/InitializeDll.h

@@ -40,7 +40,7 @@ namespace glslang {
 
 bool InitProcess();
 bool InitThread();
-bool DetachThread();
+bool DetachThread(); // TODO: use this or remove it; ideally make it unneeded
 bool DetachProcess();
 
 } // end namespace glslang