[PATCH] do not use shared extable code for ia64

[PATCH] do not use shared extable code for ia64

From: Jes Sorensen <jes@trained-monkey.org>

The new sort_extable and shared search_extable code doesn't work on ia64.
I have introduced two new #defines that archs can define to avoid the
common code being built.  ARCH_HAS_SEARCH_EXTABLE and
ARCH_HAS_SORT_EXTABLE.