Switch NULL to C++11 nullptr in source/Interpreter

Patch by Robert Matusewicz

llvm-svn: 206711
diff --git a/lldb/source/Interpreter/Property.cpp b/lldb/source/Interpreter/Property.cpp
index e5cf63a..4937626 100644
--- a/lldb/source/Interpreter/Property.cpp
+++ b/lldb/source/Interpreter/Property.cpp
@@ -56,7 +56,7 @@
             // "definition.default_cstr_value" as a string value that represents the default
             // value.
             if (definition.default_cstr_value)
-                m_value_sp.reset (new OptionValueBoolean(Args::StringToBoolean (definition.default_cstr_value, false, NULL)));
+                m_value_sp.reset (new OptionValueBoolean(Args::StringToBoolean (definition.default_cstr_value, false, nullptr)));
             else
                 m_value_sp.reset (new OptionValueBoolean(definition.default_uint_value != 0));
             break;
@@ -108,7 +108,7 @@
         {
             Format new_format = eFormatInvalid;
             if (definition.default_cstr_value)
-                Args::StringToFormat (definition.default_cstr_value, new_format, NULL);
+                Args::StringToFormat (definition.default_cstr_value, new_format, nullptr);
             else
                 new_format = (Format)definition.default_uint_value;
             m_value_sp.reset (new OptionValueFormat(new_format));