first stage of adding free/dontfree support to datadec: added token '-' (to the lexer), made optional in a parameter declaration (in the parser), made a place to store "BOOL dontfree" (in the struct module) and rules in the parser to glue it together.  also added an array of predefined types-that-are-never-freed and used that (as well as the "-") to set dontfree.