#2888 compile failed with "--with-metafont"

[Shigeharu TAKENO]

The compile of git-version of gnuplot failed with configure option "--with-metafont".

In file included from term.c:1571:
In file included from ./term.h:361:
../term/metafont.trm:529:22: error: use of undeclared identifier 'line_and_point'
529 | MF_justify_text, line_and_point, MF_arrow, set_font_null

In term/driver.h, line_and_point is defined if defined "WITH_METAFONT". But the configure set "HAVE_METAFONT" to 1, not "WITH_METAFONT". See attached patch.