* lib/setpayload.c (setpayload): On MIPS CPUs with MIPS_NAN2008_DOUBLE,
accept a zero payload.
* lib/setpayloadf.c (setpayloadf): On MIPS CPUs with MIPS_NAN2008_FLOAT,
accept a zero payload.
* lib/setpayloadl.c (setpayloadl): On MIPS CPUs with
MIPS_NAN2008_LONG_DOUBLE, accept a zero payload.
* m4/setpayload.m4 (gl_FUNC_SETPAYLOADF, gl_FUNC_SETPAYLOAD,
gl_FUNC_SETPAYLOADL): Invoke gl_NAN_MIPS.
* modules/setpayload (Files): Add m4/nan-mips.m4.
* modules/setpayloadf (Files): Likewise.
* modules/setpayloadl (Files): Likewise.