Early expression evaluation

Early expression evaluation

Folding a constant expression early can lead to loss of tokens, eg.
ABSOLUTE, that are significant in ld's horrible context sensitive
expression evaluation.  Also, MAXPAGESIZE and other "constants" may
not have taken values specified on the command line, leading to the
wrong value being cached.

	* ldexp.c (exp_unop, exp_binop, exp_trinop, exp_nameop): Don't
	fold expression.
	* testsuite/ld-elf/maxpage3b.d: Expect correct maxpagesize.