Change two windows_thread_info members to "bool"

Change two windows_thread_info members to "bool"

This changes a couple of fields of windows_thread_info to have type
"bool".  It also updates the comment of another field, to clarify the
possible values it can hold.

gdb/ChangeLog
2020-04-08  Tom Tromey  <tromey@adacore.com>

	* windows-nat.c (thread_rec)
	(windows_nat_target::fetch_registers): Update.
	* nat/windows-nat.h (struct windows_thread_info) <suspended>:
	Update comment.
	<debug_registers_changed, reload_context>: Now bool.

gdbserver/ChangeLog
2020-04-08  Tom Tromey  <tromey@adacore.com>

	* win32-i386-low.c (update_debug_registers)
	(i386_prepare_to_resume, i386_thread_added): Update.