Drop ripemd, hash256

[ajtowns]

bllsh/opcodes.py

Lines 1009 to 1011 in 5c981a5

	(0x23, "ripemd160", op_ripemd160),
	(0x24, "hash160", op_hash160),
	(0x25, "hash256", op_hash256),

No real reason to keep ripemd support (it's slow). Also, if you really want a 160bit hash, then (substr (sha256 "foo") 12) would work.

Likewise not much point having hash256; (sha256 (sha256 "foo")) seems fine.