It appears that in the Fortran 95 binding in 5.9.10, the font setting constants (PL_FCI_SANS etc.) have become variables. In bindings/f95/plplot_parameters.h we now have
integer :: PL_FCI_SANS
data PL_FCI_SANS / z'0' /
in place of

integer, parameter :: PL_FCI_SANS = z'0'

Which cannot be used in a data initialization such as:

  integer, parameter, dimension(*) :: font_list = [PL_FCI_SANS, PL_FCI_SERIF, &
       & PL_FCI_MONO, PL_FCI_SCRIPT, PL_FCI_SYMBOL]

Is there a good reason for this or is it a regression?

James