Replace std::to_string with locale-independent alternative

src/test/blockchain_tests.cpp

@@ -8,6 +8,7 @@
 
 #include <chain.h>
 #include <rpc/blockchain.h>
+#include <util/string.h>
 #include <test/util/setup_common.h>
 
 /* Equality between doubles is imprecise. Comparison should be done
@@ -30,8 +31,8 @@ static CBlockIndex* CreateBlockIndexWithNbits(uint32_t nbits)
 static void RejectDifficultyMismatch(double difficulty, double expected_difficulty) {
      BOOST_CHECK_MESSAGE(
         DoubleEquals(difficulty, expected_difficulty, 0.00001),
-        "Difficulty was " + std::to_string(difficulty)
-            + " but was expected to be " + std::to_string(expected_difficulty));
+        "Difficulty was " + ToString(difficulty)
+            + " but was expected to be " + ToString(expected_difficulty));
 }
 
 /* Given a BlockIndex with the provided nbits,