som.c reloc sanity checking

som.c reloc sanity checking

This patch checks that relocations emitted in som_write_fixups have
offsets that are monotonic and within a section.  To do that properly
using bfd_reloc_offset_in_range it is necessary to set the reloc howto
size field, which isn't used otherwise by the som backend.  Note that
the sizes used are not exactly those in the old sizing switch
statement deleted from som_write_fixups, but all relocs handled by the
main switch statement there get the same size.  Most unhandled relocs
get a zero size (exceptions being R_RELOCATION, R_SPACE_REF,
R_MILLI_REL, R_BREAKPOINT which all involve writing one word according
to my SOM reference).  I figure it doesn't matter since any unhandled
reloc is converted to 0xff R_RESERVED, and a default of zero is better
for a "don't know" reloc.

Besides tidying the code, stringizing name from type in SOM_HOWTO
fixes R_REPEATED_INIT name.

	* som.c (SOM_HOWTO): Add SIZE arg, delete NAME.  Stringize type
	to name.
	(som_hppa_howto_table): Update with sizes.
	(som_write_fixups): Delete sizing switch statement.  Sanity check
	bfd_reloc address against subsection size.