Add documentation for the SBTarget::ReadInstructions and
SBTarget::GetInstructions APIs so it's a little clearer to 
understand which should be used.

<rdar://problem/18787018>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@222225 91177308-0d34-0410-b5e6-96231b3b80d8
Fix up the code in the FuncUnwinders class that
retrieves the personality routine addr and the
LSDA addr.  Don't bother checking with the
"non-call site" unwind plan - this kind of
information is only going to come from the 
call site unwind plan.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@222226 91177308-0d34-0410-b5e6-96231b3b80d8