PR28176, rl78 complex reloc divide by zero

PR28176, rl78 complex reloc divide by zero

This is a bit more than just preventing the divide by zero.  Most of
the patch is tidying up error reporting, so that for example, linking
an object file with a reloc stack underflow produces a linker error
rather than just displaying a message that might be ignored.

	PR 28176
	* elf32-rl78.c (RL78_STACK_PUSH, RL78_STACK_POP): Delete.
	(rl78_stack_push, rl78_stack_pop): New inline functions.
	(rl78_compute_complex_reloc): Add status and error message params.
	Use new inline stack handling functions.  Report stack overflow
	or underflow, and divide by zero.
	(rl78_special_reloc): Return status and error message from
	rl78_compute_complex_reloc.
	(rl78_elf_relocate_section): Similarly.  Modernise reloc error
	reporting.  Delete unused bfd_reloc_other case.  Don't assume
	DIR24S_PCREL overflow is due to undefined function.
	(rl78_offset_for_reloc): Adjust to suit rl78_compute_complex_reloc.