Log Message:
Cosmetic change to make it easier to disable fortran.

This commit makes no semantic change; it merely splits
  USE_LANGUAGES=c fortran77
into two lines, reorders, and adds comments.

However, one can then easily turn off
  USE_LANGUAGES+= fortran77
and turn on
  CONFIGURE_ARGS+= --disable-fortran
and build, without a fortran dependency, and observe that there are no
PLIST problems.