Floating-point NaN or Infinity values should be allowed as a feature #209

Introduce 'allowSpecialFloats' for readers and 'useSpecialFloats' for writers, use consistent macro snprintf definition for writers and readers, provide new unit tests for #209

include/json/reader.h

@@ -321,6 +321,9 @@ public:
         the JSON value in the input string.
     - `"rejectDupKeys": false or true`
       - If true, `parse()` returns false when a key is duplicated within an object.
+    - `"allowSpecialFloats": false or true`
+      - If true, special float values (NaNs and infinities) are allowed 
+        and their values are lossfree restorable.
 
     You can examine 'settings_` yourself
     to see the defaults. You can also write and read them just like any

include/json/writer.h

@@ -99,6 +99,10 @@ public:
         Strictly speaking, this is not valid JSON. But when the output is being
         fed to a browser's Javascript, it makes for smaller output and the
         browser can handle the output just fine.
+    - "useSpecialFloats": false or true
+      - If true, outputs non-finite floating point values in the following way:
+        NaN values as "NaN", positive infinity as "Infinity", and negative infinity
+        as "-Infinity".
 
     You can examine 'settings_` yourself
     to see the defaults. You can also write and read them just like any