Don't use ZeroWrapLimited. Use unlimited version instead.

[tompng]

Auto limit allocation is not so good.
After several refactoring and bug fixes, ZeroWrapLimited turned out to be useless in most cases.
It allocates with extra Max(extra_sub_prec, extra_rounding_prec, extra_div_prec, extra_sqrt_prec, ...) DECDIGs. This value 2 is hardcoded.
In a few case that ZeroWrapLimited is really needed, explicitly calculate precision is enough.

// Before
NewZeroWrapLimited(1, mx + extra); // Be sure extra <= 2*BASE_FIG because NewZeroWrapLimited hardcodes 2

// After
if (prec == 0 && prec_limit) mx = prec_limit;
NewZeroWrap(1, mx + extra); // extra can be any value

Remaining NewZeroWrapLimited and NewOneNolimit is only used in sqrt and will be removed in #381