implemented (u)lltod in assembly

[ZERICO2005]

Implements (u)lltod in assembly and optimizes (u)ltod.

Since long double has 53 bits of precision, 64 bit integers may be rounded. (u)lltod can detect if rounding occurs and raise FE_INEXACT. This can be enabled/disabled with the define __lltod_signal_FE_INEXACT := 1 at the top of ltod.src. The rounding is hard coded to round-to-nearest with ties-to-even.

(u)lltod can switch between calling __lladd_1 or having it inlined.

[ZERICO2005]

On the topic of raising FE_INEXACT, I think it should only be raised if (u)ltof raises FE_INEXACT, which it currently does not. So I will disable raising FE_INEXACT in (u)lltod to be consistent with other routines.