[Backport from ReSpect] Fix Fortran API functions for string passing

Some surface function save/load API functions declared the passed
strings with the wrong data type:
   character(c_char), intent(in) :: name
instead of:
   character(c_char), intent(in) :: name(*)

(cherry picked from commit 7fc97c7384fb90f1266e59a70036667ab4fb60f6)

Author: robertodr

api/pcmsolver.f90

@@ -47,6 +47,7 @@ module pcmsolver
   public pcmsolver_print_surface_function
   public pcmsolver_save_surface_functions
   public pcmsolver_save_surface_function
+  public pcmsolver_save_surface_function_to_npz
   public pcmsolver_load_surface_function
   public pcmsolver_write_timings
 
@@ -201,6 +202,14 @@ subroutine pcmsolver_save_surface_function(context, name) bind(C)
       character(kind=c_char, len=1), intent(in) :: name(*)
     end subroutine pcmsolver_save_surface_function
 
+    subroutine pcmsolver_save_surface_function_to_npz(context, npz_name, name, suffix) bind(C)
+      import
+      type(c_ptr), value :: context
+      character(kind=c_char, len=1), intent(in) :: npz_name(*)
+      character(kind=c_char, len=1), intent(in) :: name(*)
+      character(kind=c_char, len=1), intent(in) :: suffix(*)
+    end subroutine pcmsolver_save_surface_function_to_npz
+
     subroutine pcmsolver_load_surface_function(context, name) bind(C)
       import
       type(c_ptr), value :: context