(function_arg): Add explicit checks for FIELD_DECLs.

(function_arg): Add explicit checks for FIELD_DECLs.

(mips_function_value): Add explicit checks for FIELD_DECLs, and save
them in the array FIELDS.  When returning structure with 1 float field,
enclose it in a PARALLEL and set the PARALLEL mode correctly.
* mips/mips.md (call_value): Call gen_call_value_multiple_internal0
only if there are multiple return values.  Strip the PARALLEL off
if there there is only one return value.

From-SVN: r12411