Remove HAVE_STDLIB_H

The C89 and later standard defines the `<stdlib.h>` header as part of
the standard headers [1] and on current systems it is always present
and the `HAVE_STDLIB_H` symbol can be removed.

Also Autoconf suggests doing this and relying on C89 or above [2] and [3].

[1] https://port70.net/~nsz/c/c89/c89-draft.html#4.1.2
[2] http://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/headers.m4
[3] https://www.gnu.org/software/autoconf/manual/autoconf-2.69/autoconf.html

VMS/CONFIGURE.COM

@@ -899,9 +899,6 @@ $COPY SYS$INPUT [.SRC]CONFIG.H
 /* Define to 1 if you have the <stdint.h> header file. */
 //#define HAVE_STDINT_H 1
 
-/* Define to 1 if you have the <stdlib.h> header file. */
-#define HAVE_STDLIB_H 1
-
 /* Define to 1 if you have the <strings.h> header file. */
 #define HAVE_STRINGS_H 1
 

cmake/modules/AC_HEADER_STDC.cmake

@@ -3,7 +3,6 @@
 check_include_files(dirent.h HAVE_DIRENT_H)
 check_include_files(inttypes.h HAVE_INTTYPES_H)
 check_include_files(stdint.h HAVE_STDINT_H)
-check_include_files(stdlib.h HAVE_STDLIB_H)
 check_include_files(strings.h HAVE_STRINGS_H)
 check_include_files(unistd.h HAVE_UNISTD_H)
 

configure.ac

@@ -62,7 +62,6 @@ AC_CHECK_HEADERS_ONCE(m4_flatten([
 	dirent.h
 	inttypes.h
 	stdint.h
-	stdlib.h
 	strings.h
 	unistd.h
 	sys/stat.h

src/config.h.cmake

@@ -75,9 +75,6 @@
 /* Define to 1 if you have the <stdint.h> header file. */
 #cmakedefine HAVE_STDINT_H
 
-/* Define to 1 if you have the <stdlib.h> header file. */
-#cmakedefine HAVE_STDLIB_H
-
 /* Define to 1 if you have the <strings.h> header file. */
 #cmakedefine HAVE_STRINGS_H
 

src/gd_jpeg.c

@@ -47,11 +47,6 @@
 # define HAVE_BOOLEAN
 #endif
 
-/* JCE undef symbols that we don't need anymore but which are
-   may be defined in config.h from ./configure but which are
-   redefined incompatibly in jpeglib.h */
-#undef HAVE_STDLIB_H
-
 /* 1.8.1: remove dependency on jinclude.h */
 #include "jpeglib.h"
 #include "jerror.h"

src/webpng.c

@@ -6,9 +6,7 @@
 #include <stdarg.h>
 #include <errno.h>
 #include <stdio.h>
-#ifdef HAVE_STDLIB_H
 #include <stdlib.h>
-#endif
 #include <string.h>
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>

windows/msys/Makefile

@@ -9,7 +9,7 @@ LIBVER=3.0.1
 # Misc. config flags.
 CDEFS=-DHAVE_ICONV -DHAVE_ICONV_H		\
 -DHAVE_ICONV_T_DEF -DHAVE_INTTYPES_H	\
--DHAVE_STDINT_H -DHAVE_STDLIB_H -DHAVE_VISIBILITY -DICONV_CONST
+-DHAVE_STDINT_H -DHAVE_VISIBILITY -DICONV_CONST
 
 # GnuWin32 libs should all be installed in one place.
 GNUDIR=/c/tools/GnuWin32