X86: Migrate from 'regset_from_core_section' to 'iterate_over_regset_sections'

X86: Migrate from 'regset_from_core_section' to 'iterate_over_regset_sections'

For all I386 and AMD64 targets, replace all occurrences of
regset_from_core_section by the iterator method.

gdb/ChangeLog:

	* amd64obsd-tdep.c (amd64obsd_regset_from_core_section): Remove.
	(amd64obsd_iterate_over_regset_sections): New.
	(amd64obsd_core_init_abi): Adjust gdbarch initialization.
	* i386-cygwin-tdep.c (i386_windows_regset_from_core_section):
	Remove.
	(i386_cygwin_init_abi): Clear tdep->sizeof_fpregset.  Drop
	regset_from_core_section initialization.
	* i386-tdep.c (i386_regset_from_core_section): Remove.
	(i386_iterate_over_regset_sections): New.
	(i386_gdbarch_init): Adjust gdbarch initialization.
	* i386-tdep.h (i386_regset_from_core_section): Remove prototype.
	(i386_iterate_over_regset_sections): New prototype.
	* i386obsd-tdep.c (i386obsd_aout_regset_from_core_section):
	Remove.
	(i386obsd_aout_iterate_over_regset_sections): New.
	(i386obsd_aout_init_abi): Adjust gdbarch initialization.
	* configure.tgt (gdb_target_obs): Add fbsd-tdep.o for all x86 FreeBSD
	targets.
	* amd64fbsd-tdep.c (fbsd-tdep.h): Include.
	(amd64fbsd_init_abi): Call fbsd_init_abi.
	* i386fbsd-tdep.c (fbsd-tdep.h): Include.
	(i386fbsd4_init_abi): Call fbsd_init_abi.
	* amd64fbsd-nat.c (_initialize_amd64fbsd_nat): No longer set
	target method 'make_corefile_notes'.
	* i386fbsd-nat.c (_initialize_i386fbsd_nat): Likewise.