[gdk-pixbuf] build: drop "libpng" from detected list

[Colin Walters <walters src gnome org>]

commit 91074d01a0e2b4508f7f253f1e0a7669363cb128
Author: Richard Purdie <richard purdie linuxfoundation org>
Date:   Mon Apr 15 08:06:45 2013 -0400

    build: drop "libpng" from detected list
    
    This gives us an arbitrary version depending on the build root, and we
    may not be upwards compatible with future versions.  Or it's possible
    that the ancient (but LSB mandated) 1.2 claims the "libpng.pc" name.
    
    Signed-off-by: Colin Walters <walters verbum org>

 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/configure.ac b/configure.ac
index 106fab1..5efc1b6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -586,7 +586,7 @@ fi
 
 dnl Test for libpng
   if test x$with_libpng != xno && test -z "$LIBPNG"; then
-    for l in libpng16 libpng15 libpng14 libpng12 libpng13 libpng10 libpng; do
+    for l in libpng16 libpng15 libpng14 libpng12 libpng13 libpng10; do
       AC_MSG_CHECKING(for $l)
       if $PKG_CONFIG --exists $l ; then
         AC_MSG_RESULT(yes)