Simplify RPCclient, adapt json_parse_error test

# Conflicts:
#	src/test/rpc_tests.cpp

src/rpcclient.h

@@ -9,5 +9,9 @@
 #include "univalue/univalue.h"
 
 UniValue RPCConvertValues(const std::string& strMethod, const std::vector<std::string>& strParams);
+/** Non-RFC4627 JSON parser, accepts internal values (such as numbers, true, false, null)
+ * as well as objects and arrays.
+ */
+UniValue ParseNonRFCJSONValue(const std::string& strVal);
 
 #endif // BITCOIN_RPCCLIENT_H