fix some sign warnings pointed out by gcc-4
fix some sign warnings pointed out by gcc-4

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