TMoney previously hard-wired banker's rounding (rmHalfEven) at its single
normalisation point. The underlying TDecimal already supports all eight
TRoundingMode values plus custom IRoundingStrategy, so expose that through
TMoney: every constructor and rounding-sensitive operation gains overloads
taking an explicit TRoundingMode or an IRoundingStrategy.
MoneyFromStr('1.005','USD') -> 1.00 (banker's, unchanged default)
MoneyFromStr('1.005','USD', rmHalfUp) -> 1.01
C := A.Add(B, rmCeiling);
M := MoneyFromStr('9.999','USD', myCashRoundingStrategy);
Overloaded: MoneyFromStr, MoneyFromDecimal, Add, Subtract, Multiply (each
gains a TRoundingMode form and an IRoundingStrategy form). MoneyFromInt,
MoneyZero, MultiplyInt and Negate are exact (no fraction introduced) and
need no mode. The existing no-mode calls are unchanged and keep banker's
rounding, so this is fully backward-compatible.
Internally a single MakeMoneyS(strategy) core does the normalisation; the
mode form delegates via StandardRounding(Mode) and the default via
rmHalfEven — one rounding code path.
Tests: 5 IR/semantic tests and 8 dual-backend e2e tests covering the mode
overloads (HalfUp/Down/Ceiling), the custom-strategy overload, the
default-stays-banker's guarantee, and rounding on Add/Multiply/constructors.
Docs: language-rationale.adoc updated to record that rounding is swappable
per call (default banker's), not hard-wired.
Verified: FIXPOINT_OK, NATIVE_FIXPOINT_OK, NATIVE_INTERNAL_OK; full suite
green on both the QBE-built and native-built runners (3686 tests).
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