linuxthreads.old: fix typo in pthread_mutex_unlock hidden prototype
linuxthreads.old: fix typo in pthread_mutex_unlock hidden prototype

Reported-by: Tony Wu <38d699a2ec8283e63ba2d5893eaaac3c6cd66428@gmail.com>
Signed-off-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@gentoo.org>

waweber/uclibc-clang,mephi42/uClibc,foss-xtensa/uClibc,kraj/uClibc,hjl-tools/uClibc,waweber/uclibc-clang,hwoarang/uClibc,hjl-tools/uClibc,kraj/uclibc-ng,kraj/uclibc-ng,brgl/uclibc-ng,brgl/uclibc-ng,ffainelli/uClibc,foss-xtensa/uClibc,majek/uclibc-vx32,wbx-github/uclibc-ng,hjl-tools/uClibc,groundwater/uClibc,mephi42/uClibc,skristiansson/uClibc-or1k,wbx-github/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,brgl/uclibc-ng,groundwater/uClibc,czankel/xtensa-uclibc,ddcc/klee-uclibc-0.9.33.2,kraj/uClibc,ffainelli/uClibc,waweber/uclibc-clang,majek/uclibc-vx32,ffainelli/uClibc,ddcc/klee-uclibc-0.9.33.2,hjl-tools/uClibc,ffainelli/uClibc,skristiansson/uClibc-or1k,kraj/uclibc-ng,foss-xtensa/uClibc,czankel/xtensa-uclibc,kraj/uclibc-ng,czankel/xtensa-uclibc,wbx-github/uclibc-ng,kraj/uClibc,mephi42/uClibc,majek/uclibc-vx32,czankel/xtensa-uclibc,ddcc/klee-uclibc-0.9.33.2,hjl-tools/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,hwoarang/uClibc,groundwater/uClibc,brgl/uclibc-ng,kraj/uClibc,wbx-github/uclibc-ng,ffainelli/uClibc,groundwater/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,mephi42/uClibc,skristiansson/uClibc-or1k,ddcc/klee-uclibc-0.9.33.2,skristiansson/uClibc-or1k,groundwater/uClibc,waweber/uclibc-clang,hwoarang/uClibc,hwoarang/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,majek/uclibc-vx32,foss-xtensa/uClibc