... but differently

client/mysqltest.cc:
  my_safe_print_str() don't append \n anymore
dbug/dbug.c:
  restore safemalloc as a part of dbug suite
dbug/user.r:
  restore 'S' flag documentation
include/my_dbug.h:
  restore safemalloc as a part of dbug suite
include/my_sys.h:
  move valgrind defines to a dedicated header
mysys/my_malloc.c:
  use new safemalloc
mysys/stacktrace.c:
  don't append \n. let the calller do it, if needed
sql/mysqld.cc:
  my_safe_print_str() don't append \n anymore