os: cp_r fn to copy files recursively

vlib/os/os.v

@@ -151,7 +151,40 @@ pub fn cp(old, new string) ?bool {
 	}
 }
 
-fn vfopen(path, mode string) voidptr { //*C.FILE {
+pub fn cp_r(source_path, dest_path string, overwrite bool) ?bool{
+	if !os.file_exists(source_path) {
+		return error('Source path doesn\'t exist')
+	}
+	//single file copy
+	if !os.is_dir(source_path) {
+		adjasted_path := if os.is_dir(dest_path) { 
+			filepath.join(dest_path, os.basedir(source_path)) } else { dest_path }
+		if os.file_exists(adjasted_path) {
+			if overwrite { os.rm(adjasted_path) }
+			else { return error('Destination file path already exist') }
+		}
+		os.cp(source_path, adjasted_path) or { return error(err) }
+		return true
+	}
+	if !os.is_dir(dest_path) {
+		return error('Destination path is not a valid directory')
+	}
+	files := os.ls(source_path) or { return error(err) }
+	for file in files {
+		sp := filepath.join(source_path, file)
+		dp := filepath.join(dest_path, file)
+		if os.is_dir(sp) {
+			os.mkdir(dp)
+		}
+		cp_r(sp, dp, overwrite) or {
+			os.rmdir(dp)
+			panic(err) 
+		}
+	}
+	return true
+}
+
+fn vfopen(path, mode string) *C.FILE {
 	$if windows {
 		return C._wfopen(path.to_wide(), mode.to_wide())
 	} $else {