[sanitizer] read() syscall hook.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@187414 91177308-0d34-0410-b5e6-96231b3b80d8
[sanitizer] Tweak read syscall handler signature for consistency.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@187417 91177308-0d34-0410-b5e6-96231b3b80d8