Change install_breakpoint to take a std::unique_ptr

This changes install_breakpoint to take a std::unique_ptr rvalue-ref
argument.  This makes it clear that install_breakpoint takes ownership
of the pointer, and prevents bugs like the one fixed by the previous
patch.

ChangeLog
2017-08-22  Tom Tromey  <tom@tromey.com>

	* breakpoint.h (install_breakpoint): Update.
	* breakpoint.c (add_solib_catchpoint): Update.
	(install_breakpoint): Change argument to a std::unique_ptr.
	(create_fork_vfork_event_catchpoint): Use std::unique_ptr.
	(create_breakpoint_sal, create_breakpoint): Update.
	(watch_command_1, catch_exec_command_1)
	(strace_marker_create_breakpoints_sal): Use std::unique_ptr.
	(add_to_breakpoint_chain): Change argument to a std::unique_ptr.
	Return the breakpoint.
	(set_raw_breakpoint_without_location, set_raw_breakpoint)
	(new_single_step_breakpoint): Update.
	* break-catch-throw.c (handle_gnu_v3_exceptions): Use
	std::unique_ptr.
	* break-catch-syscall.c (create_syscall_event_catchpoint): Use
	std::unique_ptr.
	* break-catch-sig.c (create_signal_catchpoint): Use
	std::unique_ptr.
	* ada-lang.c (create_ada_exception_catchpoint): Use
	std::unique_ptr.

gdb/break-catch-syscall.c

@@ -370,14 +370,13 @@ static void
 create_syscall_event_catchpoint (int tempflag, std::vector<int> &&filter,
                                  const struct breakpoint_ops *ops)
 {
-  struct syscall_catchpoint *c;
   struct gdbarch *gdbarch = get_current_arch ();
 
-  c = new syscall_catchpoint ();
-  init_catchpoint (c, gdbarch, tempflag, NULL, ops);
+  std::unique_ptr<syscall_catchpoint> c (new syscall_catchpoint ());
+  init_catchpoint (c.get (), gdbarch, tempflag, NULL, ops);
   c->syscalls_to_be_caught = std::move (filter);
 
-  install_breakpoint (0, c, 1);
+  install_breakpoint (0, std::move (c), 1);
 }
 
 /* Splits the argument using space as delimiter.  */