more C standard progress

There was a transcription error in the comments in cstd.h for
the standard list of header files, where only the description
remained for <stdlib.h>, not the name of the file itself.

Remove several extraneous inclusions of the standard C99 headers.

Tested on the following afterwards:
Linux (using hints/linux.370) including tty, curses, qt6, and X11
macOS (using hints/macOS.370) including tty, curses, qt5, and X11
Windows MSYS2 using sys/windows/GNUmakefile
Windows Visual Studio using sys/windows/Makefile.nmake
msdos cross-compile on Ubuntu using djgpp cross-compiler

sys/windows/GNUmakefile

@@ -97,6 +97,8 @@ GCC_EXTRA_WARNINGS = N
 #
 #==============================================================================
 
+$(info Using $(lastword $(MAKEFILE_LIST)))
+
 SKIP_NETHACKW = N
 USE_LUADLL = Y
 WANT_LUAC = N

sys/windows/win32api.h

@@ -30,6 +30,8 @@
 #error win32api.h should be included first
 #endif
 
+#include "config.h"
+
 #if defined(_MSC_VER)
 #pragma warning(disable : 4142) /* Warning, Benign redefinition of type */
 #pragma pack(8)
@@ -37,7 +39,6 @@
 
 #ifdef DEBUG
 #define _CRTDBG_MAP_ALLOC
-#include <stdlib.h>
 #include <crtdbg.h>
 #endif
 

sys/windows/windmain.c

@@ -10,8 +10,6 @@
 #ifdef DLB
 #include "dlb.h"
 #endif
-#include <ctype.h>
-#include <stdlib.h>
 #include <sys\stat.h>
 #include <errno.h>
 #include <ShlObj.h>

sys/windows/windsys.c

@@ -20,7 +20,6 @@
 #ifndef __BORLANDC__
 #include <direct.h>
 #endif
-#include <ctype.h>
 #ifdef TTY_GRAPHICS
 #include "wintty.h"
 #endif