+ modify mvcur() to distinguish between internal use by the ncurses
library, and external callers, preventing it from reading the content
of the screen which is only nonblank when curses calls have updated
it. This makes test/dots_mvcur.c avoid painting colored cells in
the left margin of the display.
+ minor fix to test/dots_mvcur.c
+ move configured symbols USE_DATABASE and USE_TERMCAP to term.h as
NCURSES_USE_DATABASE and NCURSES_USE_TERMCAP to allow consistent
use of these symbols in term_entry.h