Fix "maintenance selftest" printing stray instructions

The "maintenance selftest" command is printing odd bits of stray
instructions like:

~~~
brkwarning: A handler for the OS ABI "GNU/Linux" is not built into this configuration
of GDB.  Attempting to continue with the default HS settings.


brkmov  r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov       r0, #0mov   r0, #0mov       r0, #0mov       r0, #0mov       r0, #0breakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakbreakM3.L = 0xffff;/* ( -1) M3=0x0xffff(65535) */break 8break 8warning: A handler for the OS ABI "GNU/Linux" is not built into this configuration
of GDB.  Attempting to continue with the default cris:common_v10_v32 settings.
~~~

etc.  Those appear because here:

  class gdb_disassembler_test : public gdb_disassembler
  {
  public:

    const bool verbose = false;

    explicit gdb_disassembler_test (struct gdbarch *gdbarch,
				    const gdb_byte *insn,
				    size_t len)
      : gdb_disassembler (gdbarch,
			  (verbose ? gdb_stdout : &null_stream),
			  gdb_disassembler_test::read_memory),


specifically in this line:

			  (verbose ? gdb_stdout : &null_stream),

"verbose" has not been initialized yet, because the order of
initialization is base classes first, then members.  I.e. "verbose" is
only initialized after the base constructor is called.  Since the
gdb_disassembler_test object is created on the stack, "verbose" has
garbage at that point.  If the gargage is non-zero, then we end up
with the gdb_disassembler_test's stream incorrectly pointing to
gdb_stdout.

gdb/ChangeLog:
2017-02-02  Pedro Alves  <palves@redhat.com>

	* disasm-selftests.c (print_one_insn_test): Move the "verbose"
	field out of gdb_disassembler_test and make it static.

1 files changed, 1 insertions, 2 deletions

diff --git a/gdb/disasm-selftests.c b/gdb/disasm-selftests.c
index 7d0b006..9eb80b4 100644
--- a/gdb/disasm-selftests.c
+++ b/gdb/disasm-selftests.c
@@ -102,13 +102,12 @@ print_one_insn_test (struct gdbarch *gdbarch)
   /* Test gdb_disassembler for a given gdbarch by reading data from a
      pre-allocated buffer.  If you want to see the disassembled
      instruction printed to gdb_stdout, set verbose to true.  */
+  static const bool verbose = false;
 
   class gdb_disassembler_test : public gdb_disassembler
   {
   public:
 
-    const bool verbose = false;
-
     explicit gdb_disassembler_test (struct gdbarch *gdbarch,
 				    const gdb_byte *insn,
 				    size_t len)