PR# 13690 Multiple unchecked memory allocations in run-time

There are many occurrences in the run-time of what appear to be calls to 
malloc or a related routine, where the result is not checked for nullness.
This could result in reading from or writing to a null pointer instead of reporting an
"out of memory" error.  Please check the attached list (some of which are
definitely bugs) and fix any that are not dead code.  In some cases
I wasn't sure if the lack of a check was OK, so there might be some
"bugs" in my list.

I also included a few unchecked calls to fopen as a bonus.
Note that strdup and putenv allocate memory, so they must also be
checked for failure.

Here are a few more unchecked memory allocations.  I think the first one
is definitely a bug.  The others are all calls to of the form

   xxx = eif_realloc (xxx, SOME_SIZE);

If `xxx' was not NULL before the call and `eif_realloc' returns NULL,
we have a memory leak.  If you're going to use `eif_realloc' for this
sort of thing, it seems to me that a better pattern (used elsewhere in
other runtime code) is

   my_local = eif_realloc(xxx, SOME_SIZE);
   if (!my_local) {
      enomem();
   }
   xxx = my_local;

If `xxx' was already guaranteed to be NULL before the call, you should
use `eif_malloc' instead to avoid confusion.

Attachments for problem report #13690