PR 30308 again

Commit 22f8905d9f38 reintroduced pr30308.  This fix resolves equates
safely in the presence of symbol loops by using symbol_equated_to.
Symbols aren't prematurely modified, by copying their value
expressions before i386_intel_simplify does its work.  I figure that
it is safer to do this for all symbols rather than just the particular
case of equates, so the in_equate parameter can disappear.