Revert recent libpng changes.

They fix only bugs that aren't being reported, so it may be better
to do them on the trunk.
* configure.ac (PNG_CFLAGS): Remove.  All uses removed.
(LIBPNG): Don't be consistent about -lpng16 versus -lpng.
Ignore libpng-config's exit status.  Always append -lz -lm.
* src/Makefile.in (PNG_CFLAGS): Remove; all uses removed.
* src/image.c [HAVE_LIBPNG_PNG_H]: Include <libpng/png.h>, not <png.h>.

Fixes: debbugs:17339

3 files changed, 10 insertions, 2 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 15b7c202034..0f6aaf93598 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2014-05-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Revert recent libpng changes (Bug#17339).
+        * Makefile.in (PNG_CFLAGS): Remove; all uses removed.
+        * image.c [HAVE_LIBPNG_PNG_H]: Include <libpng/png.h>, not <png.h>.
+
 2014-05-03  Paul Eggert  <eggert@cs.ucla.edu>
 
         Handle systems without WCONTINUED consistently.  (Bug#15110, 17339)
diff --git a/src/Makefile.in b/src/Makefile.in
index c35e38bb290..388923596c9 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -77,7 +77,6 @@ C_SWITCH_MACHINE=@C_SWITCH_MACHINE@
 C_SWITCH_SYSTEM=@C_SWITCH_SYSTEM@
 
 GNUSTEP_CFLAGS=@GNUSTEP_CFLAGS@
-PNG_CFLAGS=@PNG_CFLAGS@
 
 ## Define C_SWITCH_X_SITE to contain any special flags your compiler
 ## may need to deal with X Windows.  For instance, if you've defined
@@ -326,7 +325,6 @@ ALL_CFLAGS=-Demacs $(MYCPPFLAGS) -I. -I$(srcdir) \
   -I$(lib) -I$(srcdir)/../lib \
   $(C_SWITCH_MACHINE) $(C_SWITCH_SYSTEM) $(C_SWITCH_X_SITE) \
   $(GNUSTEP_CFLAGS) $(CFLAGS_SOUND) $(RSVG_CFLAGS) $(IMAGEMAGICK_CFLAGS) \
-  $(PNG_CFLAGS) \
   $(LIBXML2_CFLAGS) $(DBUS_CFLAGS) $(XRANDR_CFLAGS) $(XINERAMA_CFLAGS) \
   $(SETTINGS_CFLAGS) $(FREETYPE_CFLAGS) $(FONTCONFIG_CFLAGS) \
   $(LIBOTF_CFLAGS) $(M17N_FLT_CFLAGS) $(DEPFLAGS) \
diff --git a/src/image.c b/src/image.c
index dcbe5942b32..4133aaa7621 100644
--- a/src/image.c
+++ b/src/image.c
@@ -22,8 +22,12 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <unistd.h>
 
 #ifdef HAVE_PNG
+#if defined HAVE_LIBPNG_PNG_H
+# include <libpng/png.h>
+#else
 # include <png.h>
 #endif
+#endif
 
 #include <setjmp.h>
 #include <c-ctype.h>