Find all user/system magic signature files.

        @system_only - If True, only the system magic file directory will be searched.
        @user_only   - If True, only the user magic file directory will be searched.

        Returns a list of user/system magic signature files.

def _magic_signature_files(self, system_only=False, user_only=False):
        '''
        Find all user/system magic signature files.

        @system_only - If True, only the system magic file directory will be searched.
        @user_only   - If True, only the user magic file directory will be searched.

        Returns a list of user/system magic signature files.
        '''
        files = []
        user_binarch = self._user_path(self.BINWALK_MAGIC_DIR, self.BINARCH_MAGIC_FILE)
        system_binarch = self._system_path(self.BINWALK_MAGIC_DIR, self.BINARCH_MAGIC_FILE)

        def list_files(dir_path):
            # Ignore hidden dotfiles.
            return [os.path.join(dir_path, x) for x in os.listdir(dir_path) if not x.startswith('.')]

        if not system_only:
            user_dir = os.path.join(self.user_dir, self.BINWALK_USER_DIR, self.BINWALK_MAGIC_DIR)
            files += list_files(user_dir)
        if not user_only:
            system_dir = os.path.join(self.system_dir, self.BINWALK_MAGIC_DIR)
            files += list_files(system_dir)

        # Don't include binarch signatures in the default list of signature files.
        # It is specifically loaded when -A is specified on the command line.
        if user_binarch in files:
            files.remove(user_binarch)
        if system_binarch in files:
            files.remove(system_binarch)

        return files