* corelow.c (core_close): Don't hardcode the core's pid.

	* corelow.c (core_close): Don't hardcode the core's pid.
	(core_open): Find core threads before calling
	post_create_inferior.
	(add_to_thread_list, get_core_register_section): Take into account
	systems where the regset section names encode the pid of the
	inferior.

	* gdbarch.sh (core_reg_section_encodes_pid): New gdbarch setting.
	* gdbarch.h, gdbarch.c: Regenerate.

	* amd64-sol2-tdep.c (amd64_sol2_init_abi): Set it.
	* i386-sol2-tdep.c (i386_sol2_init_abi): Set it.
	* sparc-sol2-tdep.c (sparc32_sol2_init_abi): Set it.
	* sparc64-sol2-tdep.c (sparc64_sol2_init_abi): Set it.