In codegen for PRIM_ASSIGN, allow the LHS to be a wide ref.
In codegen for PRIM_ASSIGN, allow the LHS to be a wide ref.

In some cases, this allows codegenAssign to be called with wide references on
both the LHS and RHS.  I disabled the assertion that this case never occurs and
added code to generate C code with the correct semantics in this case:  A local
buffer is allocated and the transfer is implemented as a wide get followed by a
wide put.

hildeth/chapel,hildeth/chapel,hildeth/chapel,hildeth/chapel,hildeth/chapel,hildeth/chapel,hildeth/chapel