warn unused result for bfd IO functions

warn unused result for bfd IO functions

This patch fixes all the warnings I found in bfd, binutils and ld,
plus some bitrotted COFF_GO32 code that tried to allocate -168ul
bytes.  When the malloc fail was reported these testsuite fails
resulted:

i386-go32  +FAIL: go32 stub
i386-go32  +ERROR: tcl error sourcing /home/alan/src/binutils-gdb/ld/testsuite/ld-i386/i386.exp.
i386-go32  +ERROR: couldn't open "tmpdir/go32stub": no such file or directory
i386-go32  +FAIL: ld-scripts/sane1
i386-go32  +FAIL: ld-scripts/assign-loc
i386-go32  +FAIL: ld-scripts/pr18963

This does result in some warnings in gdb which are fixed in a followup
patch.

bfd/
	* bfdio.c (bfd_read, bfd_write): Add ATTRIBUTE_WARN_UNUSED_RESULT.
	(bfd_tell, bfd_stat, bfd_seek, bfd_mmap): Likewise.
	* bfd-in2.h: Regenerate.
	* coff-rs6000.c (xcoff_write_armap_big) Don't ignore bfd_write
	return value.
	(xcoff_generate_rtinit): Likewise.  Also free data_buffer and
	string_table before returning.
	* coff64-rs6000.c (xcoff64_generate_rtinit): Likewise.
	* coff-stgo32.c (go32exe_check_format): Don't ignore bfd_seek
	return value.
	* coffcode.h (coff_apply_checksum): Don't ignore bfd_write return.
	(coff_write_object_contents <COFF_GO32>): Likewise, and bfd_malloc.
	Fix bitrotted code to look for first section with non-zero filepos.
	* elf64-ia64-vms.c (elf64_vms_write_shdrs_and_ehdr): Don't ignore
	bfd_seek or bfd_write return values.
	* pef.c (bfd_pef_scan_section): Likewise.
	(bfd_pef_read_header, bfd_pef_xlib_read_header): Likewise.
	* vms-misc.c (_bfd_vms_output_end): Likewise.  Return status.
	* vms.h (_bfd_vms_output_end): Update prototype.
	* vms-alpha.c: Pass _bfd_vms_output_end status up call chains.
	* wasm-module.c (wasm_compute_custom_section_file_position): Don't
	ignore bfd_seek or bfd_write return values.
	(wasm_compute_section_file_positions): Likewise.
	* xsym.c (bfd_sym_scan): Don't ignore bfd_seek return value.
	(bfd_sym_read_name_table): Likewise.
binutils/
	* ar.c (print_contents, extract_file): Don't ignore bfd_seek
	return value.
ld/
	* pdb.c (create_section_contrib_substream): Don't ignore bfd_seek
	return value.
	(create_section_header_stream): Likewise.
	* pe-dll.c (pe_get16, pe_get32): Add fail param to return results
	from bfd_seek and bfd_read.
	(pe_implied_import_dll): Handle these fails, and other bfd_seek
	and bfd_read return values.