Added support for amalgated source and header generation (a la sqlite). Refer to README.txt section "Generating amalgated source and header" for detail.

The amalgated sources are generated by concatenating JsonCpp source in the correct order and defining macro JSON_IS_AMALGATED to prevent inclusion of other headers. Sources and header has been modified to prevent any inclusion when this macro is defined.

The script amalgate.py handle the generation.
diff --git a/include/json/value.h b/include/json/value.h
index 14464e4..66821ab 100644
--- a/include/json/value.h
+++ b/include/json/value.h
@@ -6,7 +6,9 @@
 #ifndef CPPTL_JSON_H_INCLUDED
 # define CPPTL_JSON_H_INCLUDED
 
+#if !defined(JSON_IS_AMALGATED)
 # include "forwards.h"
+#endif // if !defined(JSON_IS_AMALGATED)
 # include <string>
 # include <vector>