* alpha-tdep.h (gdbarch_tdep): Add sigcontext_addr member.

* alpha-tdep.h (gdbarch_tdep): Add sigcontext_addr member.
* alpha-tdep.c (alpha_sigcontext_addr): New function.
(alpha_find_saved_regs): Use alpha_sigcontext_addr.
(alpha_gdbarch_init): Initialize tdep->sigcontext_addr.
* alpha-linux-tdep.c: Include frame.h.
(alpha_linux_sigcontext_addr): New function.
(alpha_linux_init_abi): Set tdep->sigcontext_addr to
alpha_linux_sigcontext_addr.
* alpha-osf1-tdep.c: Include gdbcore.h.
(alpha_osf1_sigcontext_addr): New function.
(alpha_osf1_init_abi): Set tdep->sigcontext_addr to
alpha_osf1_sigcontext_addr.
* config/alpha/tm-alpha.h (SIGCONTEXT_ADDR): Remove.
* config/alpha/tm-alphalinux.h (SIGCONTEXT_ADDR): Remove.