New sreal implementation which uses int64_t as m_sig.

gcc/ChangeLog:

2014-11-27  Martin Liska  <mliska@suse.cz>

	* sreal.c (sreal::shift_right): New implementation
	for int64_t as m_sig.
	(sreal::normalize): Likewise.
	(sreal::to_int): Likewise.
	(sreal::operator+): Likewise.
	(sreal::operator-): Likewise.
	(sreal::operator*): Likewise.
	(sreal::operator/): Likewise.
	(sreal::signedless_minus): Removed.
	(sreal::signedless_plus): Removed.
	* sreal.h (sreal::operator<): New implementation
	for int64_t as m_sig.