Log Message:
Update to mtools-4.0.18.

Improvements since the 4.0.17 release are:

        Fix for names of iconv encodings on AIX
        Fix mt_size_t on NetBSD
        Fixed compilation on Mingw
        Fixed doc (especially mformat)
        Fix mformat'ing of FAT12 filesystems with huge cluster sizes
        Minfo prints image file name in mformat command line if an image
        file name was given
        Always generate gzip-compressed RPMs, in order to remain
        compatible with older distributions
        Fixed buffer overflow with drive letter in mclasserase