* regset.c: Tweak comment.

* regset.c: Tweak comment.
(regset_alloc): Remove descr argument.  Use GDBARCH_OBSTACK_ZALLOC
macro.
* regset.h: Update copyright year.
(struct regset): Remove `descr' member, add `gdbarch' member.
(regset_alloc): Adjust prototype and comment.
* i386-tdep.c (i386_supply_gregset): Get TDEP from REGSET->arch.
(i386_supply_fpregset): Likewise.
(i386_regset_from_core_section): Update call to regset_alloc.
* i386obsd-tdep.c (i386obsd_aout_supply_regset): Get TDEP from
REGSET->arch.
(i386obsd_aout_regset_from_core_section): Update call to
regset_alloc.
* i386nbsd-tdep.c (i386nbsd_aout_supply_regset): Get TDEP from
REGSET->arch.
(i386nbsd_aout_regset_from_core_section): Update call to
regset_alloc.
* amd64-tdep.c (amd64_supply_fpregset): Get TDEP from
REGSET->arch.
(amd64_regset_from_core_section): Update call to regset_alloc.
* amd64obsd-tdep.c (amd64obsd_supply_regset): Get TDEP from
REGSET->arch.
(amd64obsd_regset_from_core_section): Update call to regset_alloc.
* sparcnbsd-tdep.c (sparc32nbsd_supply_gregset): Directly pass
&sparc32nbsd_gregset in sparc32_supply_gregset call.
(sparc32nbsd_init_abi): Update call to regset_alloc.
* sparc64obsd-tdep.c (sparc64obsd_supply_gregset): Directly pass
&sparc64obsd_core_gregset in sparc64_supply_gregset call.
(sparc64obsd_init_abi): Update call to regset_alloc.
* sparc64nbsd-tdep.c (sparc64nbsd_supply_gregset): Directly pass
&sparc64nbsd_gregset in sparc64_supply_gregset call.
(sparc64nbsd_init_abi): Update call to regset_alloc.
* sparc64fbsd-tdep.c (sparc64fbsd_supply_gregset): Directly pass
&sparc64fbsd_gregset in sparc64_supply_gregset call.
(sparc64fbsd_init_abi): Update call to regset_alloc.