Cycles: Remove compatibility code for OSL-1.4

That code was mainly needed for the transition period, now we've
got all platforms updated to new OSL.

Plus there are some crucial fixes baking in the current upstream
sources which we'll need to have for the next Blender release.

intern/cycles/render/osl.cpp

@@ -248,10 +248,6 @@ void OSLShaderManager::shading_system_free()
 
 bool OSLShaderManager::osl_compile(const string& inputfile, const string& outputfile)
 {
-#if OSL_LIBRARY_VERSION_CODE < 10500
-	typedef string string_view;
-#endif
-
 	vector<string_view> options;
 	string stdosl_path;
 	string shader_path = path_get("shader");
@@ -748,11 +744,7 @@ OSL::ShadingAttribStateRef OSLCompiler::compile_type(Shader *shader, ShaderGraph
 
 	current_type = type;
 
-#if OSL_LIBRARY_VERSION_CODE >= 10501
 	OSL::ShadingAttribStateRef group = ss->ShaderGroupBegin(shader->name.c_str());
-#else
-	ss->ShaderGroupBegin(shader->name.c_str());
-#endif
 
 	ShaderNode *output = graph->output();
 	set<ShaderNode*> dependencies;
@@ -780,13 +772,7 @@ OSL::ShadingAttribStateRef OSLCompiler::compile_type(Shader *shader, ShaderGraph
 
 	ss->ShaderGroupEnd();
 
-#if OSL_LIBRARY_VERSION_CODE >= 10501
 	return group;
-#else
-	OSL::ShadingAttribStateRef group = ss->state();
-	ss->clear_state();
-	return group;
-#endif
 }
 
 void OSLCompiler::compile(OSLGlobals *og, Shader *shader)