unifdef: implement err.h funcs locally
unifdef: implement err.h funcs locally

Since the err.h functions are optional in uClibc, make sure we can rebuild
ourselves if support is disabled.

URL: https://bugs.busybox.net/show_bug.cgi?id=257
Reported-by: Michael Deutschmann <17b9e1c64588c7fa6419b4d29dc1f4426279ba01@talamasca.ocis.net>
Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

czankel/xtensa-uclibc,ddcc/klee-uclibc-0.9.33.2,foss-xtensa/uClibc,m-labs/uclibc-lm32,groundwater/uClibc,majek/uclibc-vx32,ndmsystems/uClibc,hwoarang/uClibc,groundwater/uClibc,kraj/uClibc,wbx-github/uclibc-ng,hjl-tools/uClibc,wbx-github/uclibc-ng,kraj/uClibc,gittup/uClibc,ysat0/uClibc,skristiansson/uClibc-or1k,hwoarang/uClibc,skristiansson/uClibc-or1k,gittup/uClibc,OpenInkpot-archive/iplinux-uclibc,kraj/uClibc,wbx-github/uclibc-ng,waweber/uclibc-clang,ffainelli/uClibc,mephi42/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,gittup/uClibc,czankel/xtensa-uclibc,foss-xtensa/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,gittup/uClibc,waweber/uclibc-clang,OpenInkpot-archive/iplinux-uclibc,atgreen/uClibc-moxie,ffainelli/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,ysat0/uClibc,ddcc/klee-uclibc-0.9.33.2,ffainelli/uClibc,brgl/uclibc-ng,czankel/xtensa-uclibc,majek/uclibc-vx32,majek/uclibc-vx32,brgl/uclibc-ng,hjl-tools/uClibc,OpenInkpot-archive/iplinux-uclibc,kraj/uClibc,ndmsystems/uClibc,czankel/xtensa-uclibc,foss-xtensa/uClibc,ndmsystems/uClibc,hwoarang/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,foss-xtensa/uClibc,ffainelli/uClibc,hwoarang/uClibc,mephi42/uClibc,atgreen/uClibc-moxie,groundwater/uClibc,OpenInkpot-archive/iplinux-uclibc,atgreen/uClibc-moxie,ysat0/uClibc,ddcc/klee-uclibc-0.9.33.2,ffainelli/uClibc,waweber/uclibc-clang,m-labs/uclibc-lm32,groundwater/uClibc,majek/uclibc-vx32,skristiansson/uClibc-or1k,mephi42/uClibc,hjl-tools/uClibc,kraj/uclibc-ng,mephi42/uClibc,waweber/uclibc-clang,kraj/uclibc-ng,atgreen/uClibc-moxie,ddcc/klee-uclibc-0.9.33.2,hjl-tools/uClibc,brgl/uclibc-ng,kraj/uclibc-ng,groundwater/uClibc,wbx-github/uclibc-ng,m-labs/uclibc-lm32,m-labs/uclibc-lm32,brgl/uclibc-ng,ndmsystems/uClibc,kraj/uclibc-ng,ysat0/uClibc,hjl-tools/uClibc,skristiansson/uClibc-or1k