Get rid of malloc.h.

This is a non-POSIX/ISO-C header.  It is ok to include this on Linux, but it
is obsolete on BSD; FreeBSD even throws an error if you include it with
__STDC__ defined.  Every system should nowadays have malloc() defined in
stdlib.h.

Diff is largely mechanical, replacing malloc.h with stdlib.h where it is not
yet included anyway.

cde/programs/dthelp/parser/pass2/util/context.c

@@ -156,7 +156,7 @@ delim.h.
 */
 
 #include <stdio.h>
-#include <malloc.h>
+#include <stdlib.h>
 #if defined(MSDOS)
 #include <process.h>
 #endif

cde/programs/dthelp/parser/pass2/util/conutil.c

@@ -30,7 +30,7 @@ This product and information is proprietary of Tandem Computers Incorporated.
 /* Conutil has utility procedures for program CONTEXT. */
 #include <stdio.h>
 #include <string.h>
-#include <malloc.h>
+#include <stdlib.h>
 #if defined(MSDOS)
 #include <process.h>
 #endif

cde/programs/dthelp/parser/pass2/util/fclndir.c

@@ -35,7 +35,7 @@ with an error code of 0 if the files are the same, 1 if they differ, and
 */
 
 #include <stdio.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <string.h>
 #if defined(MSDOS)
 #include <process.h>

cde/programs/dthelp/parser/pass2/util/malloc.c

@@ -26,7 +26,7 @@
 /* Interfaces to free and malloc with optional debugging traces */
 
 /**/
-#include <malloc.h>
+#include <stdlib.h>
 #include <stdio.h>
 #if defined(MSDOS)
 #include <process.h>