Log Message:
Pullup ticket #6003 - requested by gutteridge
x11/libxfceui: build fix

Revisions pulled up:
- x11/libxfce4ui/Makefile                                       1.20

---
   Module Name:    pkgsrc
   Committed By:   gutteridge
   Date:           Fri Jul  5 14:52:41 UTC 2019

   Modified Files:
           pkgsrc/x11/libxfce4ui: Makefile

   Log Message:
   libxfce4ui: set C99 dependency

   Address build breakage noted in Joyent CentOS bulk builds.