CL_MACH_VM configure check will fail with future compilers

The functions vm_allocate and task_self are not declared, so they are only found (at link time) if compilation succeed due to compiler support for implicit function declarations. Compilers are going to remove such support by default.

AC_DEFUN([CL_MACH_VM],
[
  CL_LINK_CHECK([vm_allocate], [cl_cv_func_vm], ,
    [vm_allocate(); task_self();],
    [AC_DEFINE([HAVE_MACH_VM],,[have vm_allocate() and task_self() functions])])
])