C# bindings generator cleanup

- Normal log messages are no longer warnings.
- BindingsGenerator is no longer a singleton.
- Added a log function.

modules/mono/utils/string_utils.cpp

@@ -32,6 +32,8 @@
 
 #include "core/os/file_access.h"
 
+#include <stdio.h>
+
 namespace {
 
 int sfind(const String &p_text, int p_from) {
@@ -184,3 +186,50 @@ Error read_all_file_utf8(const String &p_path, String &r_content) {
 	r_content = source;
 	return OK;
 }
+
+// TODO: Move to variadic templates once we upgrade to C++11
+
+String str_format(const char *p_format, ...) {
+	va_list list;
+
+	va_start(list, p_format);
+	String res = str_format(p_format, list);
+	va_end(list);
+
+	return res;
+}
+// va_copy was defined in the C99, but not in C++ standards before C++11.
+// When you compile C++ without --std=c++<XX> option, compilers still define
+// va_copy, otherwise you have to use the internal version (__va_copy).
+#if !defined(va_copy)
+#if defined(__GNUC__)
+#define va_copy(d, s) __va_copy((d), (s))
+#else
+#define va_copy(d, s) ((d) = (s))
+#endif
+#endif
+
+#if defined(MINGW_ENABLED) || defined(_MSC_VER)
+#define vsnprintf vsnprintf_s
+#endif
+
+String str_format(const char *p_format, va_list p_list) {
+	va_list list;
+
+	va_copy(list, p_list);
+	int len = vsnprintf(NULL, 0, p_format, list);
+	va_end(list);
+
+	len += 1; // for the trailing '/0'
+
+	char *buffer(memnew_arr(char, len));
+
+	va_copy(list, p_list);
+	vsnprintf(buffer, len, p_format, list);
+	va_end(list);
+
+	String res(buffer);
+	memdelete_arr(buffer);
+
+	return res;
+}