Minimize mutex usage when in single threaded mode.

src/parser.cpp

@@ -750,6 +750,7 @@ gb_internal Ast *ast_matrix_index_expr(AstFile *f, Ast *expr, Token open, Token
 gb_internal Ast *ast_ident(AstFile *f, Token token) {
 	Ast *result = alloc_ast_node(f, Ast_Ident);
 	result->Ident.token = token;
+	result->Ident.hash = string_hash(token.string);
 	return result;
 }