Miscellaneous memory alloc related fixes

Miscellaneous memory alloc related fixes

Some minor tidies.  Allocating memory for internal relocs and symbols
after reading external relocs is slightly better with fuzzed files.
You can at least do something about silly sizes that way.

	* aoutx.h (slurp_reloc_table): Allocate reloc_cache after
	reading external relocs.
	* ecoff.c (ecoff_slurp_reloc_table): Likewise.
	* archive.c (_bfd_write_archive_contents): Don't twiddle bfd_error
	after bfd_bread.
	* archive64.c (_bfd_archive_64_bit_slurp_armap): Remove unnecessary
	bfd_release.
	* elf32-m32c.c (m32c_offset_for_reloc): Make shndx_buf a bfd_byte*.
	(m32c_elf_relax_section): Likewise.
	* elf32-rl78.c (rl78_offset_for_reloc): Likewise.
	(rl78_elf_relax_section): Likewise.
	* elf32-rx.c (rx_offset_for_reloc): Likewise.
	(elf32_rx_relax_section): Likewise.
	* mach-o.c (bfd_mach_o_alloc_and_read): Move earlier with better
	parameter types and use..
	(bfd_mach_o_read_dylinker, bfd_mach_o_read_dylib),
	(bfd_mach_o_read_fvmlib, bfd_mach_o_read_str): ..in these functions.
	* peicode.h (pe_bfd_object_p): Don't zero the part of opthdr
	being read from file, just the extra.
	* som.c (som_slurp_symbol_table): Allocate internal symbol buffer
	after reading external syms.  Free on failure.