Load/store whole register instructions have mop=00

vmv.v.v isn't actually a HINT

Fix definition of first-fault loads w.r.t. nonzero vstart

Elements [vl, VMAX-1] may be clobbered when vta=1.
Clarify this, and avoid the uppercase HINT, which implies that
architectural state is not modified.

The old definition ("vl is reduced to the number of elements processed")
is only true when vstart=0, since elements [0, vstart-1] are not processed.

Closes #512.

Closes #509.

Closes #508.

Closes #503.

Discussed in issue #503.

Still needs detailed arithmetic and exceptional case handling.

Factor out handlng of scalar floating-point values, and cases where FLEN != EEW into vector arithmetic encoding section.
Closes #409.

Add assembly pseudoinstructions vncvt.x.x.v

Closes #396.

Closes #374

not interrupts.

Add note that fault-only-first instructions should change vstart not vl on an interrupt.
Closes #359.

Closes #348.

Closes #459.