Reading errno within pthreads always resulted in 0 breaking various programs
like transmission and collectd. This patch is not 100% thread safe but it brings
back threading into a usable state for now.
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@23905 3c298f89-4303-0410-b956-a3cf2f4a3e73
