RFC: Deprecate the ARM simulator

Hi Guys,

   I would like to deprecate or even delete the ARM simulator.

   Although I am listed as the maintainer for the sim, I have not
   made any improvements to it for years and it is completely
   unable to handle modern ARM cores.  The only updates to the
   sources in the last few years have been to fix compilation
   issues, and basically it has bit-rotted away.

   It is not entirely clear to me how a sim target should be
   deprecated.  I am attaching a patch that shows one possible
   method - adding code to the sim/configure.ac file to indicate
   that the target is deprecated.  An alternative would be to
   add the sim target to the noconfigdirs list that is constructed
   in the top level configure.ac file.  Although I think that
   that list is for components that do not support the target at
   all, rather than components where the target is deprecated.

   Anyway, thoughts, comments, suggestions ?

Cheers
   Nick

diff --git a/sim/configure.ac b/sim/configure.ac
index fad5b71ee59..e9ec6e70efc 100644
--- a/sim/configure.ac
+++ b/sim/configure.ac
@@ -84,6 +84,18 @@ m4_define([SIM_TARGET], [dnl
   AM_CONDITIONAL([SIM_ENABLE_ARCH_$2], [${sim_enable_arch_$2}])
 ])
 
+case $target in
+ arm*-*-* | \
+ null)
+    if test "x$enable_obsolete" != xyes; then
+      echo "*** Configuration $targ is obsolete." >&2
+      echo "*** Specify --enable-obsolete to build it anyway." >&2
+      echo "*** Support will be REMOVED in the next major release of GDB," >&2
+      echo "*** unless a maintainer comes forward." >&2
+      exit 1
+    fi;;
+esac
+
 dnl WHEN ADDING ENTRIES TO THIS MATRIX:
 dnl Make sure that the left side always has two dashes.  Otherwise you can get
 dnl spurious matches.  Even for unambiguous cases, do this as a convention, else