Added initial tests for --glsl-version

- Added compilation tests for shader stages using a different
  version at each stage.

Test/glsl.versionOverride.geom

@@ -0,0 +1,16 @@
+/*
+
+glslangValidator.exe --glsl-version 430 -V -S geom -o glsl.versionOverride.geom.out glsl.versionOverride.geom
+
+*/
+
+#version 330
+
+layout (points) in;
+layout (line_strip, max_vertices = 2) out;
+
+void main() {    
+    EmitVertex();
+    EmitVertex();   
+    EndPrimitive();
+}