Consult libpng-config more consistently.

* configure.ac (edit_cflags): Move this up and to the top level,
so that PNG_CFLAGS can use it too.
(PNG_CFLAGS): New var.
(png_longjmp): Use PNG_CFLAGS when checking.
(LIBPNG): Be consistent about -lpng16 etc; e.g., don't use -lpng16
in some places and -lpng in others.  Test libpng-config's exit
status.  If it succeeds, use its output rather than appending -lz -lm.
* src/Makefile.in (PNG_CFLAGS): New var.
(ALL_CFLAGS): Use it.
* src/image.c [HAVE_PNG]: Don't worry about <libpng/png.h>, as
CFLAGS now handles this.

Fixes: debbugs:17339

1 files changed, 0 insertions, 4 deletions

diff --git a/src/image.c b/src/image.c
index 4133aaa7621..dcbe5942b32 100644
--- a/src/image.c
+++ b/src/image.c
@@ -22,12 +22,8 @@ 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>