Improve Z flag handling on H8

Improve Z flag handling on H8

This patch improves handling of the Z bit in the status register in a
variety of ways to improve either the code size or code speed on various
H8 subtargets.

For example, we can test the zero/nonzero status of the upper byte of a
16 bit register using mov.b, we can move the Z or an inverted Z into a
QImode register profitably on some subtargets.  We can move Z or an
inverted Z into the sign bit on the H8/SX profitably, etc.

gcc/

	* config/h8300/h8300.md (HSI2): New iterator.
	(eqne_invert): Similarly.
	* config/h8300/testcompare.md (testhi_upper_z): New pattern.
	(cmpqi_z, cmphi_z, cmpsi_z): Likewise.
	(store_z_qi, store_z_i_qi, store_z_hi, store_z_hi_sb): New
	define_insn_and_splits and/or define_insns.
	(store_z_hi_neg, store_z_hi_and, store_z_<mode>): Likewise.
	(store_z_<mode>_neg, store_z_<mode>_and, store_z): Likewise.