Kind of hokey, but errno.h drags in misc/sys/param.h which
defines MIN/MAX causing an error. Include system headers
first to grab MIN/MAX definition in param.h, and define
HAVE_ALLOCA to preserve existing behavior.
* sysdeps/ieee754/ldbl-128ibm/mpn2ldl.c: Include gmp headers
after system headers to prevent MIN/MAX redefinition. Define
HAVE_ALLOCA to preserve builtin alloca usage.