Previously, libmount only read error messages from fsopen() file descriptor. This commit improves the library to read all messages and keep them in their original format ("<type> <mesg>") in the library mount context. Applications can now read all messages by using mnt_context_get_mesgs(). Furthermore, private functions have been implemented to include new library-specific messages in the log. Currently, these messages are only managed in mnt_context_get_excode(), but it would be beneficial to relocate them to the appropriate locations where errors are triggered. In the future, mnt_context_get_excode() should only be utilized by basic applications that require an one error message. For more critical purposes (e.g. mount(8)), it will be recommended to utilize the messages array. The public function mnt_context_get_excode() has been modified to use the new functionality and provide messages in a backwardly compatible way. Signed-off-by: Karel Zak <kzak@redhat.com>