sigchain: add wrappers for sigaction64/sigprocmask64.

Add wrappers for sigaction64/sigprocmask64 and switch the storage of
chained handlers to sigaction64.

Bug: http://b/73108155
Test: treehugger
Change-Id: If0f1f254541ab4b6d218b97914e68fd3e8f00705
6 files changed