Added all standard intrinsics (up to Fortran 2008)

Source: Appendix A of "Modern Fortran Explained" by Metcalf/Reid/Cohen, first published 2011

I also removed an entry "lenlge", which isn't a function in any Fortran compiler (standard or otherwise), and looks like a typo from a previous commit (i.e. a missing space).

I assume the menagerie of extra "intrinsic" functions is just to maintain some sense of compatibility with functions removed from the standard, or "common" vendor extensions. I'd definitely be in favour at some point of moving *all* the functions outside the standard into the ```user_functions``` list; I'll do it myself if there's any interest, or if there are no objections.