nvc0/ir: add emission of dadd/dmul/dmad opcodes, fix minmax

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
HACK nvc0/ir: populate shader header bit indicating fp64

HACK ALERT: this should figure out if the shader's doing fp64 stuff and
use that to populate the header.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: no instruction can load a double immediate

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: add support for new TGSI double opcodes

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>