Makefile.in.in: Turn {POFILES,DISTFILES}DEPS into yes/no options
Preserve the previous behavior even if a user forgot to update
Makevars, after calling autopoint.
* Makevars (PO_DEPENDS_ON_POT): Rename from POFILESDEPS and turn
it into a yes/no option.
(DIST_DEPENDS_ON_POT): Rename from DISTFILESDEPS and turn it into
a yes/no option.