[clang-tidy] Pass by value with std::move

Found with modernize-pass-by-value

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/Variant.cpp

@@ -27,6 +27,7 @@
 #include <cmake.h>
 #include <sstream>
 #include <algorithm>
+#include <utility>
 #include <stdio.h>
 #include <math.h>
 #include <stdlib.h>
@@ -127,9 +128,9 @@ Variant::Variant (const double value)
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-Variant::Variant (const std::string& value)
+Variant::Variant (std::string  value)
 : _type (Variant::type_string)
-, _string (value)
+, _string (std::move(value))
 {
 }