Introduce and use gdb_file_up

Introduce and use gdb_file_up

This introduces gdb_file_up, a unique pointer holding a FILE*, and
then changes some code in gdb to use it.  In particular
gdb_fopen_cloexec now returns a gdb_file_up.  This allow removing some
cleanups.

ChangeLog
2017-08-03  Tom Tromey  <tom@tromey.com>

	* xml-support.c (xml_fetch_content_from_file): Update.
	* ui-file.c (stdio_file::open): Update.
	* tracefile-tfile.c (tfile_start): Update.
	* remote.c (remote_file_put, remote_file_get): Update.
	* nat/linux-procfs.c (linux_proc_get_int)
	(linux_proc_pid_get_state, linux_proc_tid_get_name): Update.
	* nat/linux-osdata.c (linux_common_core_of_thread): Update.
	(command_from_pid, commandline_from_pid, linux_xfer_osdata_cpus)
	(print_sockets, linux_xfer_osdata_shm, linux_xfer_osdata_sem)
	(linux_xfer_osdata_msg, linux_xfer_osdata_modules): Update.
	* nat/linux-btrace.c (linux_determine_kernel_start): Update.
	* linux-nat.c (linux_proc_pending_signals): Update.
	* dwarf2read.c (write_psymtabs_to_index): Use gdb_file_up.
	(file_closer): Remove.
	* compile/compile.c (compile_to_object): Update.
	* common/filestuff.h (struct gdb_file_deleter): New.
	(gdb_file_up): New typedef.
	(gdb_fopen_cloexec): Change return type.
	* common/filestuff.c (gdb_fopen_cloexec): Return gdb_file_up.
	* cli/cli-dump.c (fopen_with_cleanup): Remove.
	(dump_binary_file, restore_binary_file): Update.
	* auto-load.c (auto_load_objfile_script_1): Update.