Introduce current_klongsize in addition to current_wordsize

Introduce current_klongsize in addition to current_wordsize

Subsequent commits are going to use current_klongsize
as the tracee's size of kernel_ulong_t type.

* defs.h (PERSONALITY0_KLONGSIZE): New macro.
[X86_64] (PERSONALITY2_KLONGSIZE): Likewise.
[SUPPORTED_PERSONALITIES > 1] (PERSONALITY1_KLONGSIZE): Likewise.
[SUPPORTED_PERSONALITIES == 1] (current_klongsize): Likewise.
[SUPPORTED_PERSONALITIES == 2 && PERSONALITY0_KLONGSIZE ==
PERSONALITY1_KLONGSIZE] (current_klongsize): Likewise.
[SUPPORTED_PERSONALITIES != 1 && (SUPPORTED_PERSONALITIES != 2 ||
PERSONALITY0_KLONGSIZE != PERSONALITY1_KLONGSIZE)] (current_klongsize):
New variable prototype.
* syscall.c [!current_klongsize] (current_klongsize): New variable.
[!current_klongsize] (personality_klongsize): New array.
(set_personality) [!current_klongsize]: Update current_klongsize
with the appropriate value from personality_klongsize.