[tracker] configure: Do not hardcode dep on libpng

[Carlos Garnacho <carlosg src gnome org>]

commit f92690092670e4dc3493513cd1a1d4d4c690aed5
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Aug 10 13:20:07 2016 +0200

    configure: Do not hardcode dep on libpng
    
    There is a --enable/disable-png check below.

 configure.ac |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index f24d084..70be144 100644
--- a/configure.ac
+++ b/configure.ac
@@ -230,7 +230,7 @@ LIBGRSS_REQUIRED=0.7
 NETWORK_MANAGER_REQUIRED=0.8
 GSTREAMER_REQUIRED=0.10.31
 GUPNP_DLNA_REQUIRED=0.9.4
-LIBPNG_REQUIRED=0.89
+LIBPNG_REQUIRED=1.2
 LIBMEDIAART_REQUIRED=1.9.0
 
 # 3.6.11 for sqlite_backup API
@@ -248,11 +248,6 @@ GOBJECT_INTROSPECTION_CHECK([0.9.5])
 GLIB_PREFIX="`$PKG_CONFIG --variable=prefix glib-2.0`"
 AC_SUBST(GLIB_PREFIX)
 
-# Check for libpng 1.2 or higher
-PKG_CHECK_MODULES(LIBPNG, [libpng >= 1.2])
-AC_SUBST(LIBPNG_CFLAGS)
-AC_SUBST(LIBPNG_LIBS)
-
 # Check requirements for gvdb
 GVDB_REQUIRED="glib-2.0 >= $GLIB_REQUIRED"
 PKG_CHECK_MODULES(GVDB, [$GVDB_REQUIRED])