implement realloc() for MONITOR_HEAP or vice versa

Add new routine 're_alloc()' that functions as MONITOR_HEAP-aware
libc realloc().  'nhrealloc()' is the version that passes source
file and line info if built with MONITOR_HEAP enabled.  The heaplog
data might now contain '<' (freed by realloc), '>' (replacement
allocation by realloc), and '*' (resized by realloc) entries in
addition to the previous '+' (allocated) and '-' (freed) entries.
heaputil has already been updated in the NHinternal repository.

Move FITSint_() and FITSuint_() from hacklib.c to alloc.c so that
they can be accessed by miscellaneous utility programs.

Remove three or four copies of FITSint_() that were duplicated in
utility programs like dlb and tile2bmp due to those not having
access to src/hacklib.o.  They do have access to src/alloc.o (and
util/panic.o).

util/makedefs.c

@@ -2351,14 +2351,4 @@ struct attribs attrmax, attrmin;
 #endif
 #endif /* STRICT_REF_DEF */
 
-/* In hacklib.c, but we don't have that and it calls panic() */
-unsigned
-FITSuint_(unsigned long long i, const char *file, int line){
-unsigned ret = (unsigned)i;
-if (ret != i) {
-    Fprintf(stdout, "Overflow at %s:%d\n", file, line);
-    makedefs_exit(EXIT_FAILURE);
-}
-return (unsigned)i;
-}
 /*makedefs.c*/