top: end reliance on strdup not failing & roll our own

Lately, top has begun to rely more and more on dynamic
memory allocations rather than the static buffers that
were found in many of its structures. This was perhaps
most evident in the increasing use of the strdup call.

This commit trades that function call for the internal
equivalent which will protect us from malloc failures.

(everything is perfectly justified plus right margins)
(are completely filled, but of course it must be luck)

Signed-off-by: Jim Warner <james.warner@comcast.net>

top/top.h

@@ -631,6 +631,7 @@ typedef struct WIN_t {
 /*------  Low Level Memory/Keyboard/File I/O support  --------------------*/
 //atic void         *alloc_c (size_t num);
 //atic void         *alloc_r (void *ptr, size_t num);
+//atic char         *alloc_s (const char *str);
 //atic inline int    ioa (struct timespec *ts);
 //atic int           ioch (int ech, char *buf, unsigned cnt);
 //atic int           iokey (int init);