Consolidate UnixSignals setting/getting in Process.

See http://reviews.llvm.org/D5108 for details.

This change does the following:

* eliminates the Process::GetUnixSignals() virtual method and replaces with a fixed getter.
* replaces the Process UnixSignals storage with a shared pointer.
* adds a Process constructor variant that can be passed the UnixSignalsSP. When the constructor without the UnixSignalsSP is specified, the Host's default UnixSignals is used.
* adds a host-specific version of GetUnixSignals() that is used when we need the host's appropriate UnixSignals variant.
* replaces GetUnixSignals() overrides in PlatformElfCore, ProcessGDBRemote, ProcessFreeBSD and ProcessLinux with code that appropriately sets the Process::UnixSignals for the process.

This change also enables some future patches that will enable llgs to be used for local Linux debugging.

llvm-svn: 216748
diff --git a/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp b/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp
index 858d8ae..f340631 100644
--- a/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp
+++ b/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp
@@ -70,8 +70,8 @@
 //------------------------------------------------------------------------------
 // Constructors and destructors.
 
-ProcessPOSIX::ProcessPOSIX(Target& target, Listener &listener)
-    : Process(target, listener),
+ProcessPOSIX::ProcessPOSIX(Target& target, Listener &listener, UnixSignalsSP &unix_signals_sp)
+    : Process(target, listener, unix_signals_sp),
       m_byte_order(lldb::endian::InlHostByteOrder()),
       m_monitor(NULL),
       m_module(NULL),
@@ -878,12 +878,6 @@
     return status;
 }
 
-UnixSignals &
-ProcessPOSIX::GetUnixSignals()
-{
-    return m_signals;
-}
-
 //------------------------------------------------------------------------------
 // Utility functions.