Fix building with glibc-2.16+ 

Upstream glibc dropped 'struct siginfo' and now there is only 'siginfo_t'. 

This fix comes from the gperftools project: 
https://code.google.com/p/gperftools/source/detail?r=176

Review URL: https://codereview.chromium.org/12388060


git-svn-id: http://linux-syscall-support.googlecode.com/svn/trunk/lss@18 829466d3-f3f5-3ae4-62ad-de35cf9bba21