[gtk+] Revert "Work around a pkg-config bug"

[Matthias Clasen <matthiasc src gnome org>]

commit afa2bc8b8d84925762fb9ba0a824024f9a237928
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun May 10 01:05:52 2015 -0400

    Revert "Work around a pkg-config bug"
    
    This reverts commit 57751fa391fce8b9f208c41260e8968dd4cdc800.
    
    I've been told that this is not, in fact, a pkg-config bug,
    but a pkg-config feature.

 configure.ac |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index bf8316e..e73c986 100644
--- a/configure.ac
+++ b/configure.ac
@@ -348,8 +348,7 @@ backend_immodules=
 have_gio_unix=no
 GDK_BACKENDS=
 GDK_EXTRA_LIBS=
-# expoxy.pc has Cflags: -I${includedir}, but pkg-config swallows that :-(
-GDK_EXTRA_CFLAGS="-I${prefix}/include"
+GDK_EXTRA_CFLAGS=
 GDK_WINDOWING=
 PANGO_PACKAGES="pango pangocairo"