[gimp] libgimp: fix Win32 build with Dr. MinGW.

[Jehan Pagès <jehanp src gnome org>]

commit 81a062f06fb40457cf64e24c21fce0e104a16caf
Author: Jehan <jehan girinstud io>
Date:   Sun Jun 12 03:36:05 2016 +0200

    libgimp: fix Win32 build with Dr. MinGW.
    
    GIMPDIR and GIMP_USER_VERSION macros need to be defined in libgimp now.

 libgimp/Makefile.am |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/libgimp/Makefile.am b/libgimp/Makefile.am
index c08c300..00242b2 100644
--- a/libgimp/Makefile.am
+++ b/libgimp/Makefile.am
@@ -67,6 +67,8 @@ endif
 gimpincludedir = $(includedir)/gimp-$(GIMP_API_VERSION)/libgimp
 
 AM_CPPFLAGS = \
+       -DGIMPDIR=\""$(gimpdir)"\"                              \
+       -DGIMP_USER_VERSION=\"$(GIMP_USER_VERSION)\"            \
        -DG_LOG_DOMAIN=\"LibGimp\"      \
        -DGIMP_COMPILATION              \
        -I$(top_srcdir)                 \