Reinstate CPR using system library.

vendor/CPR/cpr/parameters.cpp

@@ -0,0 +1,10 @@
+#include "cpr/parameters.h"
+
+#include <initializer_list>
+#include <string>
+
+#include "cpr/util.h"
+
+namespace cpr {
+Parameters::Parameters(const std::initializer_list<Parameter>& parameters) : CurlContainer<Parameter>(parameters) {}
+} // namespace cpr