xen trouble in the pkgsrc 2019Q4 branch

[Greg Troxel <gdt%lexort.com@localhost>]

On netbsd-8 amd64:

The xenkernel packages all build.

xentools4.2 fails with:

  ocamlc -g -I ../mmap -w F -warn-error F -c -o xenctrl.cmo xenctrl.ml
  File "xenctrl.ml", line 267, characters 44-45:
  267 |           let wd = Unix.write fd s 0 (String.length s) in
                                                    ^
  Error: This expression has type bytes but an expression was expected of type
           string

xentools4.8 fails with:

  /tmp/work/sysutils/xentools48/work/.buildlink/include/epoxy/egl_generated.h:10:29: fatal error: EGL/eglplatform.h: No such file or directory

which is the same issue as 4.11.

It would be nice if someone hoisted the patch to 4.11 to 4.8.