And also make xrealloc and xmalloc weak symbols so that we don't
have this problem:

 /usr/lib/gcc/x86_64-redhat-linux/4.4.1/../../../../lib64/libiberty.a(xmalloc.o):
 In function `xrealloc':
 (.text+0xc0): multiple definition of `xrealloc'
 libperf.a(wrapper.o):/home/acme_unencrypted/git/linux-2.6-tip/tools/perf/util/wrapper.c:67:
 first defined here
 collect2: ld returned 1 exit status
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1259071517-3242-4-git-send-email-acme@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>