Fix {get,set}rlimit decoding with unreliable SIZEOF_RLIM_T

When strace is built with large file support definitions in CFLAGS (as
may be provided by buildroot) the C library headers may expose a 64-bit
rlim_t even though the struct rlimit fields used by the system call
interface are only 32-bit.  The SIZEOF_RLIM_T will then be 8 which
results in bad decoding of the getrlimit and setrlimit syscalls.

This is fixed by replacing unreliable SIZEOF_RLIM_T based checks with
checks for current_wordsize.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>