28 wasted bits in a symbol

[Richard Stallman]

I see that 4 bits of flags have been added to a symbol, making it a
whole word longer.  That is a significant price to pay and I wonder if
there are alternatives.  It is clear that indirect_variable could be
replaced with some Lisp_Misc special data type stored in the value slot.
Maybe the other 3 flags can be avoided too.

I think we should make an effort to eliminate these bits and reduce
the size by a word.  Can people please look for ways to do it?