abort() to internal_error()

[Michael Elizabeth Chastain]

> (gdb) pwd
> internal_error: /a/b/c/d/foo.c:47: function calls abort ()
> ....

Fine with me.

If this happens on my workstation, I don't care whether I get
internal_error or a core dump or whatever, I'm going to start debugging
gdb either way.

If this happens on a user's desktop, I prefer the "internal_error"
form, because I'll get "/a/b/c/d/foo.c:47" in the bug report.
I imagine the user either won't care, or will prefer internal_error.

I have a side comment: I've gotten two gdb core dumps in the past month.
Both of them are cycles in the type tree which lead to recursive
death in "maint print symbols".  (One was gdb/15, fixed, and the other
is in gdb/7, not analyzed yet).  So you are still going to get core
dumps even after this change.

But that is a separate issue.

Michael