fix #32775 and #34023, issues showing kw and parameters exprs

[JeffBezanson]

This attempts to track where = expressions are parsed with head kw and show them correctly, using fallback Expr(...) printing when necessary. Also handles ; in tuples, since that is closely related.

fix #32775
fix #34023

[vtjnash]

Is it worthwhile to print an extra block expression for Expr(:call, :call, :(a = 2)), which has the same syntax meaning though a different parse structure:

call( (a = 2;) )

[JeffBezanson]

That's clever! I think it's better to print the exact structure whenever possible though, even if that means using the ugly $(Expr(...)). Should come up rarely enough.