Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Use sysctl KERN_PROC_SIGTRAMP to retrieve the signal trampoline
location for the native amd64 ABI. This fixes unwinding over the
signal frame after trampoline was moved to the shared page.

The code would be more correct if using sysctl for the target process
instead of inspecting gdb' own trampoline, but the current change is
least intrusive and currently, we always initialize the native ABI
sysvec first, which means that trampoline location for FreeBSD/amd64
ABI is relatively stable.

Similar change will benefit libunwind.

Analyzed by: avg
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

This commit was generated by cvs2svn to compensate for changes in r130803,
which included commits to RCS files with non-trunk default branches.

Import of GDB version 6.1.1 (stripped; see FREEBSD-Xlist rev. 1.6).