Adds support for utf paths on Windows.

Not all file formats/calls are supported yet. It will be expended.

Please from now on use BLI_fopen, BLI_* for file manipulations.
For non-windows systems BLI_fopen just calls fopen.
For Windows, the utf-8 string is translated to utf-16 string in order to call UTF version of the function.

source/blender/editors/space_text/text_ops.c

@@ -460,7 +460,7 @@ static void txt_write_file(Text *text, ReportList *reports)
 	BLI_strncpy(filepath, text->name, FILE_MAX);
 	BLI_path_abs(filepath, G.main->name);
 	
-	fp= fopen(filepath, "w");
+	fp= BLI_fopen(filepath, "w");
 	if(fp==NULL) {
 		BKE_reportf(reports, RPT_ERROR, "Unable to save \"%s\": %s", filepath, errno ? strerror(errno) : "Unknown error writing file");
 		return;