Ensure that the fact that a float was provided on input is preserved when writing output; update tests to reflect this fact

src/lib_json/json_writer.cpp

@@ -139,7 +139,7 @@ namespace {
 JSONCPP_STRING valueToString(double value, bool useSpecialFloats, unsigned int precision) {
   // Allocate a buffer that is more than large enough to store the 16 digits of
   // precision requested below.
-  char buffer[32];
+  char buffer[36];
   int len = -1;
 
   char formatString[6];
@@ -150,6 +150,12 @@ JSONCPP_STRING valueToString(double value, bool useSpecialFloats, unsigned int p
   // concepts of reals and integers.
   if (isfinite(value)) {
     len = snprintf(buffer, sizeof(buffer), formatString, value);
+    
+    // try to ensure we preserve the fact that this was given to us as a double on input
+    if (!strstr(buffer, ".") && !strstr(buffer, "e")) {
+      strcat(buffer, ".0");
+    }
+
   } else {
     // IEEE standard states that NaN values will not compare to themselves
     if (value != value) {