Make *_name fields char * instead of char[]. Specify desired

Make *_name fields char * instead of char[]. Specify desired
width of output in printf() rather than "%-*s" and sizeof(name) +
1.  Clearer, may even save some bytes as many names are shorter
than the max.

Rename PRT_print_mbrtypes() to PRT_print_mbrmenu() and
PRT_print_gpttypes() to PRT_print_gptmenu() to remove implied
completeness of list presented in menu.

No functional change.