Migrate core source files to C++. Add yaml-cpp project as dependency (#2207)

By updating to this commit, Linux users have to regenerate Makefiles by re-running the configure script.

* Added yaml-cpp project as a 3rdparty library
* Migrated source files core to C++
* Updated configure scripts
* Make Linux installations compile *.cpp files
* Made server components' main source file C++
* Also made headers CPP-aware.

* Added basic C wrapper for yaml-cpp library
* YAML-node path is delimited by periods.
* Basic integer types and string are supported.
* Strings returned from this wrapper have to be freed with malloc.h::aFree
* Arrays (sequence) is supported with iterator wrapper.
* Remember to free every wrapper you create!

* Add yaml-cpp as dependency of common project
* Made the repo not ignore *.yml files

Thanks to @aleos89 and @Lemongrass3110.

3rdparty/yaml-cpp/src/convert.cpp

@@ -0,0 +1,75 @@
+#include <algorithm>
+
+#include "yaml-cpp/node/convert.h"
+
+namespace {
+// we're not gonna mess with the mess that is all the isupper/etc. functions
+bool IsLower(char ch) { return 'a' <= ch && ch <= 'z'; }
+bool IsUpper(char ch) { return 'A' <= ch && ch <= 'Z'; }
+char ToLower(char ch) { return IsUpper(ch) ? ch + 'a' - 'A' : ch; }
+
+std::string tolower(const std::string& str) {
+  std::string s(str);
+  std::transform(s.begin(), s.end(), s.begin(), ToLower);
+  return s;
+}
+
+template <typename T>
+bool IsEntirely(const std::string& str, T func) {
+  for (std::size_t i = 0; i < str.size(); i++)
+    if (!func(str[i]))
+      return false;
+
+  return true;
+}
+
+// IsFlexibleCase
+// . Returns true if 'str' is:
+//   . UPPERCASE
+//   . lowercase
+//   . Capitalized
+bool IsFlexibleCase(const std::string& str) {
+  if (str.empty())
+    return true;
+
+  if (IsEntirely(str, IsLower))
+    return true;
+
+  bool firstcaps = IsUpper(str[0]);
+  std::string rest = str.substr(1);
+  return firstcaps && (IsEntirely(rest, IsLower) || IsEntirely(rest, IsUpper));
+}
+}
+
+namespace YAML {
+bool convert<bool>::decode(const Node& node, bool& rhs) {
+  if (!node.IsScalar())
+    return false;
+
+  // we can't use iostream bool extraction operators as they don't
+  // recognize all possible values in the table below (taken from
+  // http://yaml.org/type/bool.html)
+  static const struct {
+    std::string truename, falsename;
+  } names[] = {
+      {"y", "n"}, {"yes", "no"}, {"true", "false"}, {"on", "off"},
+  };
+
+  if (!IsFlexibleCase(node.Scalar()))
+    return false;
+
+  for (unsigned i = 0; i < sizeof(names) / sizeof(names[0]); i++) {
+    if (names[i].truename == tolower(node.Scalar())) {
+      rhs = true;
+      return true;
+    }
+
+    if (names[i].falsename == tolower(node.Scalar())) {
+      rhs = false;
+      return true;
+    }
+  }
+
+  return false;
+}
+}