commands/memtools: Add memtool module with memory allocation stress-test

When working on memory, it's nice to be able to test your work.

Add a memtest module. When compiled with --enable-mm-debug, it exposes
3 commands:

 * lsmem - print all allocations and free space in all regions
 * lsfreemem - print free space in all regions

 * stress_big_allocs - stress test large allocations:
  - how much memory can we allocate in one chunk?
  - how many 1MB chunks can we allocate?
  - check that gap-filling works with a 1MB aligned 900kB alloc + a
     100kB alloc.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Reviewed-by: Robbie Harwood <rharwood@redhat.com>

configure.ac

@@ -1520,6 +1520,7 @@ else
   MM_DEBUG=0
 fi
 AC_SUBST([MM_DEBUG])
+AM_CONDITIONAL([COND_MM_DEBUG], [test x$MM_DEBUG = x1])
 
 AC_ARG_ENABLE([cache-stats],
 	      AS_HELP_STRING([--enable-cache-stats],