vm_size_t and rlim_t may not be the same type.

Fixes commit 802b0eba519b1333c639fd0e1b55222099df9263
("hurd: implement RLIMIT_AS against Mach RPCs")

Check for VM limit RPCs

  * config.h.in: add #undef for HAVE_MACH_VM_GET_SIZE_LIMIT and
    HAVE_MACH_VM_SET_SIZE_LIMIT.
  * sysdeps/mach/configure.ac: use mach_RPC_CHECK to check for
    vm_set_size_limit and vm_get_size_limit RPCs in gnumach.defs.
  * sysdeps/mach/configure: regenerate file.

Use vm_get_size_limit to initialize RLIMIT_AS

  * hurd/hurdrlimit.c(init_rlimit): use vm_get_size_limit to initialize
    RLIMIT_AS entry of the _hurd_rlimits array.

Notify the kernel of the new VM size limits

  * sysdeps/mach/hurd/setrlimit.c: use the vm_set_size_limit RPC,
    if available, to notify the kernel of the new limits. Retry RPC
    calls if they were interrupted by a signal.
Message-ID: <03fb90a795b354a366ee73f56f73e6ad22a86cda.1755220108.git.dnietoc@gmail.com>

I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.

I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah.  I don't
know why I run into these diagnostics whereas others evidently do not.

remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines

hurd initialization stages use RUN_HOOK to run various initialization
functions.  That is however using absolute addresses which need to be
relocated, which is done later by csu.  We can however easily make the
linker compute relative addresses which thus don't need a relocation.
The new SET_RELHOOK and RUN_RELHOOK macros implement this.

I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master

Libc has actually been using mach's lock-internal.h mutex for a long
time already.