Adjust for renaming of Linux sigcontext offset macros.
(check_rbs_switch): Handle Linux-case only if abi_marker==ABI_MARKER_LINUX_SIGTRAMP.
(update_frame_state): For cursor's with a non-zero abi_marker, do special
Linux or HP-UX sigtramp handling as appropriate.
Clear abi_marker instead of is_signal_frame.
(Logical change 1.84)
original stack-pointer from c->sigcontext_loc.
Handle rbs-switches for Linux signal deliver on alternate signal stack and
for general case, indicated by UNW_PI_FLAG_IA64_RBS_SWITCH.
Call rbs_underflow() when we detect a register-backing-store underflow.
(Logical change 1.40)