Fix -var-update for registers in frames 1 and up

Fix -var-update for registers in frames 1 and up

XXX palves:

Watchpoints on locals are quite similar in principle with varobjs on
locals.  Likewise wathpoints/varobjs on registers.

So this actually makes "watch $pc" in non-current frames be a local
watchpoint.

So

 up
 watch $pc
 down
 continue

now does the "right" thing.  I'm not sure this is really right,
though.

Haven't done anything on the varobjs side.

gdb/testsuite/ChangeLog:
2016-06-13  Don Breazeal  <dbreazea@my.domain.org>

	* gdb.ada/mi_interface.exp: Add thread-id field to expected
	output of -var-create and -var-list-children.
	* gdb.ada/mi_var_array.exp: Add thread-id field to expected
	output of -var-list-children.
	* gdb.mi/mi-break.exp (test_error): Add thread-id field to
	expected output of -var-create.
	* gdb.mi/mi-frame-regs.exp: New test script.
	* gdb.mi/mi-var-cmd.exp: Add thread-id field to expected
	output of -var-create.
	* gdb.mi/mi-var-create-rtti.exp: Likewise.

gdb/ChangeLog:
2016-06-13  Don Breazeal  <donb@codesourcery.com>
	    Andrew Burgess <andrew.burgess@embecosm.com>

	* varobj.c (varobj_create): Initialize innermost_block to
	the global block instead of NULL.
	(new_root_variable): Initialize the thread_id and next
	fields.
	(value_of_root_1): Set within_scope if the variable's
	valid_block field is the global block.