My previous change to keep the Xtensa property tables from being GC'ed exposed 
another problem.  If the first entry in a property table is removed by the 
linker's relaxation, the relocation for the entry was getting its offset set to 
a negative value.  The subsequent call to elf_xtensa_discard_info_for_section 
was compounding the problem by neglecting to sort the relocations.  (They should 
normally be sorted following relaxation, but relaxation is not always enabled.) 
  While working on this, I decided to make the relaxation code more robust with 
regard to relocations on the property table entries, and I also added some new 
predicates to check for the various kinds of property tables.  Tested with the 
testsuite for an xtensa-elf target, and by building "busybox" for 
xtensa-linux-gnu.  Committed on the mainline.

bfd/
	* elf32-xtensa.c (xtensa_is_insntable_section): New.
	(xtensa_is_proptable_section): New.
	(elf_xtensa_discard_info_for_section): Handle "full" .xt.prop property
	tables with 12-byte entries, as well as tables with 8-byte entries.
	Sort the relocations before examining them.
	(relax_property_section): Use xtensa_is_proptable_section and
	xtensa_is_littable_section.  Rewrite code for combining table entries
	to be more robust in case of unexpected relocations.  Do not set offset
	of unused relocations to less than zero.
	(xtensa_is_property_section): Use other functions instead of
	duplicating section name comparisons.
	(xtensa_is_littable_section): Use CONST_STRNEQ for ".gnu.linkonce.p.".
	(xtensa_get_property_predef_flags): Use xtensa_is_insntable_section.