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is obsolete on BSD; FreeBSD even throws an error if you include it with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/lib/pam/libpam/pam_framework.c

@@ -44,7 +44,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <string.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #include <security/pam_appl.h>

cde/lib/pam/libpam/pam_framework_utils.c

@@ -34,7 +34,7 @@
 #include <sys/stat.h>
 #include <utmpx.h>
 #include <string.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <unistd.h>
 #include <libintl.h>
 #include <synch.h>