Bug-fix in ugetstr(): keypad "Del" key (at least in SDL-Windows mode) was

inserting an ASCII char 127 into the string rather that deleting the current
character (or the selected string, as the case may be). There was already a
translation from DEL to CIO_KEY_DC ("For compatibility with terminals lacking
special keys") in ulist(), but this translation did not exit in ugetstr(). I'm
sure if sdl_getch()'s behavior is expected/correct, but in any case, this fix
seemed to be the most appropriate.