fp-bit.c (pack_d): When using paired doubles to implement a long double...

	* config/fp-bit.c (pack_d): When using paired doubles to implement
	a long double, round the high part separately.
	(unpack_d): Fix the case in which the high part is a power of two
	and the low part is a nonzero value of the opposite sign.

From-SVN: r76780