compiler/arm/float: Fix missed part of complex-float support.

  * Enable the (now formerly commented-out) complex float move-arg
support.

  * This was commented out when originally introduced because we
originally only handled non-complex floats.  A simple oversight.
compiler/arm/{macros,float}: Introduce non-complex float MOVE macros.

  * By analogy with the integer-register MOVE macro, introduce
MOVE-SINGLE and MOVE-DOUBLE macros, as an initial step towards
simplifying the VOP definitions in the floating-point support.
compiler/arm/{macros,float}: Introduce complex float MOVE macros.

  * Second verse, same as the first: add a macro to cover up the
excess noise involved in complex-float register-register moves.
compiler/arm/sap: Define float SAP-REF and %SET-SAP-REF VOPs.

  * Basic stuff.  Switch from optional to keyword args in
DEF-SYSTEM-REF-AND-SET, add a new arg to bring in LIP (since the
float operations are register + unaligned word offset addressing,
and don't allow register + register), set up the appropriate float
load, store, and move instructions, and re-enable the disabled
bits in code/target-sap.
compiler/arm/values: Implement VOP %%NIP-VALUES.

  * This is the last of the IR2TRAN bits that we disabled with an
outright ERROR message.  VOP implementation cribbed from MIPS with
some inspiration from PPC.