Fix misc. source comment typos

Found using `codespell -q 3 -S ./thirdparty,*.po -L ang,ba,cas,dof,doubleclick,fave,hist,leapyear,lod,nd,numer,ois,paket,seeked,sinc,switchs,te,uint -D ~/Projects/codespell/codespell_lib/data/dictionary.txt `

modules/gdscript/gdscript.cpp

@@ -99,7 +99,7 @@ GDScriptInstance *GDScript::_create_instance(const Variant **p_args, int p_argco
 #endif
 	instance->owner->set_script_instance(instance);
 
-	/* STEP 2, INITIALIZE AND CONSRTUCT */
+	/* STEP 2, INITIALIZE AND CONSTRUCT */
 
 #ifndef NO_THREADS
 	GDScriptLanguage::singleton->lock->lock();

modules/gdscript/gdscript_compiler.cpp

@@ -2064,7 +2064,7 @@ Error GDScriptCompiler::_parse_class_blocks(GDScript *p_script, const GDScriptPa
 					}
 					instance->owner->set_script_instance(instance);
 
-					/* STEP 2, INITIALIZE AND CONSRTUCT */
+					/* STEP 2, INITIALIZE AND CONSTRUCT */
 
 					Variant::CallError ce;
 					p_script->initializer->call(instance, NULL, 0, ce);

modules/gdscript/gdscript_parser.cpp

@@ -1207,7 +1207,7 @@ GDScriptParser::Node *GDScriptParser::_parse_expression(Node *p_parent, bool p_s
 					if (_get_completable_identifier(COMPLETION_INDEX, identifier)) {
 
 						if (identifier == StringName()) {
-							identifier = "@temp"; //so it parses allright
+							identifier = "@temp"; //so it parses alright
 						}
 						completion_node = op;