Refactor Unix signals.

Summary:
- Consolidate Unix signals selection in UnixSignals.
- Make Unix signals available from platform.
- Add jSignalsInfo packet to retrieve Unix signals from remote platform.
- Get a copy of the platform signal for each remote process.
- Update SB API for signals.
- Update signal utility in test suite.

Reviewers: ovyalov, clayborg

Subscribers: chaoren, jingham, labath, emaste, tberghammer, lldb-commits

Differential Revision: http://reviews.llvm.org/D11094

llvm-svn: 242101

lldb/source/API/SBProcess.cpp

@@ -912,14 +912,10 @@ SBProcess::Signal (int signo)
 SBUnixSignals
 SBProcess::GetUnixSignals()
 {
-    SBUnixSignals sb_unix_signals;
-    ProcessSP process_sp(GetSP());
-    if (process_sp)
-    {
-        sb_unix_signals.SetSP(process_sp);
-    }
+    if (auto process_sp = GetSP())
+        return SBUnixSignals{process_sp};
 
-    return sb_unix_signals;
+    return {};
 }
 
 void