Merge branch 'master' into 'master'

Fix configure detection of Gimp

See merge request sane-project/frontends!19

configure.in

@@ -124,7 +124,7 @@ if test "${USE_GUI}" = "yes"; then
     fi
 
     if test "${USE_GIMP}" = "yes"; then
-        PKG_CHECK_MODULES([GIMP], [gimp-2.0], HAVE_GIMP=yes)
+        PKG_CHECK_MODULES([GIMP], [gimp-2.0], HAVE_GIMP=yes, HAVE_GIMP=no)
 	if test "${HAVE_GIMP}" = "yes"; then
 	    AC_DEFINE([HAVE_LIBGIMP_GIMP_H], 1, [Define to 1 if you have the <libgimp/gimp.h> header file.])
 	fi
@@ -145,8 +145,6 @@ if test "${USE_GUI}" = "yes"; then
   fi
 fi
 
-AC_DEFINE([HAVE_LIBGIMP_GIMP_H], 1, [Define to 1 if you have the <libgimp/gimp.h> header file.])
-
 BINPROGS=${BINPROGS}" "${GUIPROGS}
 
 AC_SUBST(INCLUDES)