Convert int to bool in agent.c

Convert int to bool in agent.c

Also moves an int declaration inside the for loop.

Code cleanup, no change in behavior intended.

gdb/ChangeLog:

2019-10-31  Christian Biesinger  <cbiesinger@google.com>

	* gdbsupport/agent.c (debug_agent): Change type to bool.
	(use_agent): Likewise.
	(all_agent_symbols_look_up): Likewise.
	(agent_loaded_p): Change return value to bool.
	(agent_look_up_symbols): Update.
	(agent_capability_check): Change return value to bool.
	* gdbsupport/agent.h (agent_loaded_p): Likewise.
	(debug_agent): Change type to bool.
	(use_agent): Likewise.
	(agent_capability_check): Change return value to bool.

gdb/gdbserver/ChangeLog:

2019-10-31  Christian Biesinger  <cbiesinger@google.com>

	* ax.h (debug_agent): Remove duplicate declaration.

Change-Id: Icb28a65fcc8c7108bcd59287e6be66bf56f8ccb5