Upon request from the gdb-maintainers, add support for keeping the
unwind-table in remote memory.  This can be faster if the unwind-table
is large and only a few entries from the table need to be read.  Such
remote tables are handled via a new unwind-table format called
UNW_INFO_FORMAT_TABLE (see libunwind-dynamic.h).  The API remains
backwards-compatible with the exception of the ia64-specific
_Uia64_find_dyn_list() function.

BKrev: 3fc3d8cd4VXFifyDtAfkKgGAR7NcnA