add attribute_unused and include features.h so that we can include libc-internal.h directly and have it work
add attribute_unused and include features.h so that we can include libc-internal.h directly and have it work

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