This will allow x86-64 to shrink its exception tables by half, and ia64 to
drop its custom implementation.
v2: Adjust arch/x86/kernel/test_nx.c (leading to some tests no longer
getting run on x86-64) and indent some pre-processor directives in
patch #2.
1/3: x86-64: use macros to generate exception table entries
2/3: x86-64: use relative 32-bit pointers in exception tables
3/3: ia64: drop custom exception table implementation
Signed-off-by: Jan Beulich <[email protected]>