Fix compilation error for powerpc32
Fix compilation error for powerpc32

Fix the following compilation error for powerpc32 platform when using
latest glibc.
error: ‘siginfo_t’ was not declared in this scope

alk/gperftools,acmorrow/gperftools,gperftools/gperftools,rzinsly/gperftools,romange/gperftools,alk/gperftools,rzinsly/gperftools,xiaoyur347/gperftools,romange/gperftools,acmorrow/gperftools,gperftools/gperftools,xiaoyur347/gperftools,romange/gperftools,alk/gperftools,acmorrow/gperftools,acmorrow/gperftools,gperftools/gperftools,gperftools/gperftools,alk/gperftools,rzinsly/gperftools,rzinsly/gperftools,romange/gperftools,xiaoyur347/gperftools,xiaoyur347/gperftools