Make lldb -Werror clean for -Wstring-conversion

Also found/fixed one bug identified by this warning in
RenderScriptx86ABIFixups.cpp where a string literal was being used in an
effort to provide a name for an instruction/register, but was instead
being passed as the bool 'isVolatile' parameter.

llvm-svn: 291198
diff --git a/lldb/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp b/lldb/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
index dae33f6..a757bba 100644
--- a/lldb/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
+++ b/lldb/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
@@ -480,8 +480,7 @@
 
     default:
       // The only valid thread resume states are listed above
-      assert(!"invalid thread resume state");
-      break;
+      llvm_unreachable("invalid thread resume state");
     }
   }