* alpha-nat.c, irix4-nat.c, irix5-nat.c, mipsv4-nat.c,

	* alpha-nat.c, irix4-nat.c, irix5-nat.c, mipsv4-nat.c,
	sparc-tdep.c (supply_gregset, supply_fpregset):  Fill inaccessible
	registers with zero to handle recent read_register_bytes change.
	* irix4-nat.c, irix5-nat.c, mipsv4-nat.c (supply_gregset,
	fill_gregset):  Fix handling of CAUSE_REGNUM.
	* mips-nat.c (store_inferior_registers):  Handle unwritable
	registers when storing a single register.
	* config/mips/tm-irix3.h (CAUSE_REGNUM, BADVADDR_REGNUM):
	Fix definitions.

	* mdebugread.c (parse_symbol, psymtab_to_symtab_1):  Clear
	allocated mips_extra_func_info, if the debug info is corrupt,
	the PDR to fill it in might be missing.