Add lldb-gdbserver support for Linux x86_64.

This change brings in lldb-gdbserver (llgs) specifically for Linux x86_64.
(More architectures coming soon).

Not every debugserver option is covered yet.  Currently
the lldb-gdbserver command line can start unattached,
start attached to a pid (process-name attach not supported yet),
or accept lldb attaching and launching a process or connecting
by process id.

The history of this large change can be found here:
https://github.com/tfiala/lldb/tree/dev-tfiala-native-protocol-linux-x86_64

Until mid/late April, I was not sharing the work and continued
to rebase it off of head (developed via id tfiala@google.com).  I switched over to
user todd.fiala@gmail.com in the middle, and once I went to github, I did
merges rather than rebasing so I could share with others.

llvm-svn: 212069
diff --git a/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp b/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp
index 94892b1..031405a 100644
--- a/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp
+++ b/lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp
@@ -934,3 +934,16 @@
     }
     return is_running;
 }
+
+const DataBufferSP
+ProcessPOSIX::GetAuxvData ()
+{
+    // If we're the local platform, we can ask the host for auxv data.
+    PlatformSP platform_sp = m_target.GetPlatform ();
+    if (platform_sp && platform_sp->IsHost ())
+        return lldb_private::Host::GetAuxvData(this);
+
+    // Somewhat unexpected - the process is not running locally or we don't have a platform.
+    assert (false && "no platform or not the host - how did we get here with ProcessPOSIX?");
+    return DataBufferSP ();
+}