* alpha-tdep.h (struct gdbarch_tdep): Add members `sc_pc_offset',

* alpha-tdep.h (struct gdbarch_tdep): Add members `sc_pc_offset',
`sc_regs_offset' and `sc_fpregs_offset'.
* alpha-tdep.c (SIGFRAME_PC_OFF, SIGFRAME_REGSAVE_OFF,
SIGFRAME_FPREGSAVE_OFF): Remove defines.
(alpha_sigtramp_register_address): Rewrite to use new members of
`struct gdbarch_tdep'.
(alpha_gdbarch_init): Initialize new members of struct
gdbarch_tdep'.
* alphafbsd-tdep.c (alphafbsd_use_struct_convention): Use
ALPHA_REGISTER_SIZE instead of DEPRECATED_REGISTER_SIZE.
(alphafbsd_sigtramp_start, alphafbsd_sigtramp_end): Nre variables.
(alphafbsd_pc_in_sigtramp): Implement.
(alphafbsd_sigtramp_offset): New function.
(alphafbsd_sigcontext_addr): New function.
(alphafbsd_init_abi): Initialize signal trampoline related members
of `struct gdbarch_tdep'.
(_initialize_alphafbsd_tdep): Add prototype.