Add a new 'eRegisterInLiveRegisterContext' RegisterLocation to track
a register value that is live in the stack frame 0 register context.

Fixes a problem where retrieving a register value on stack frame #n
would involved O(n!) stack frame checks.  This could be very slow on
a deep stack when retrieving register values that had not been
modified/saved by any of the stack frames.  Not common, but annoying
when it was hit.

<rdar://problem/19010211> 

llvm-svn: 223843
diff --git a/lldb/source/Plugins/Process/Utility/UnwindLLDB.h b/lldb/source/Plugins/Process/Utility/UnwindLLDB.h
index eb54003..35d85e2 100644
--- a/lldb/source/Plugins/Process/Utility/UnwindLLDB.h
+++ b/lldb/source/Plugins/Process/Utility/UnwindLLDB.h
@@ -48,7 +48,8 @@
             eRegisterSavedAtMemoryLocation,     // register is saved at a specific word of target mem (target_memory_location)
             eRegisterInRegister,                // register is available in a (possible other) register (register_number)
             eRegisterSavedAtHostMemoryLocation, // register is saved at a word in lldb's address space
-            eRegisterValueInferred              // register val was computed (and is in inferred_value)
+            eRegisterValueInferred,             // register val was computed (and is in inferred_value)
+            eRegisterInLiveRegisterContext      // register value is in a live (stack frame #0) register
         };
         int type;
         union