Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/CPR/include/cpr/util.h

@@ -0,0 +1,40 @@
+#ifndef CPR_UTIL_H
+#define CPR_UTIL_H
+
+#include <fstream>
+#include <string>
+#include <vector>
+
+#include "cpr/callback.h"
+#include "cpr/cookies.h"
+#include "cpr/cprtypes.h"
+#include "cpr/curlholder.h"
+
+namespace cpr {
+namespace util {
+
+Header parseHeader(const std::string& headers, std::string* status_line = nullptr,
+                   std::string* reason = nullptr);
+Cookies parseCookies(curl_slist* raw_cookies);
+size_t readUserFunction(char* ptr, size_t size, size_t nitems, const ReadCallback* read);
+size_t headerUserFunction(char* ptr, size_t size, size_t nmemb, const HeaderCallback* header);
+size_t writeFunction(char* ptr, size_t size, size_t nmemb, std::string* data);
+size_t writeFileFunction(char* ptr, size_t size, size_t nmemb, std::ofstream* file);
+size_t writeUserFunction(char* ptr, size_t size, size_t nmemb, const WriteCallback* write);
+#if LIBCURL_VERSION_NUM < 0x072000
+int progressUserFunction(const ProgressCallback* progress, double dltotal, double dlnow,
+                         double ultotal, double ulnow);
+#else
+int progressUserFunction(const ProgressCallback* progress, curl_off_t dltotal, curl_off_t dlnow,
+                         curl_off_t ultotal, curl_off_t ulnow);
+#endif
+int debugUserFunction(CURL* handle, curl_infotype type, char* data, size_t size,
+                      const DebugCallback* debug);
+std::vector<std::string> split(const std::string& to_split, char delimiter);
+std::string urlEncode(const std::string& s);
+std::string urlDecode(const std::string& s);
+
+} // namespace util
+} // namespace cpr
+
+#endif