[PATCH users/roland/safe-ctype] Uniformly put `#include "safe-ctype.h"` last among #include directives

[Roland McGrath]

The libc++ headers changed recently such that some standard C++
headers that didn't used
to lead to using <ctype.h> and its symbols now do so.

This ran afoul of the shenanigans in "safe-ctype.h" in at least one
place where that header
is included before a standard header.

This only broke things that I saw in gdb/minsyms.c, but the same
problem may well arise
in the future with other headers.  This sort of redefinition of
standard symbols is definitely not
kosher under the C and C++ standards at all.  In the long run we
should consider ways to solve
the problem "safe-ctype.h" exists to solve without violating the
language standards in this way.

To make the code more future-proof while we're still doing this, I
changed all the uses
uniformly throughout the repo to just put #include "safe-ctype.h"
last, with a comment
reminding folks not to change that ordering (and a comment in
safe-ctype.h about that).

I didn't touch anything in the libiberty subdirectory since AIUI
that's still copied from
the gcc repository.

The changes are on the users/roland/safe-ctype branch on sourceware.  My mailer
makes it difficult to paste a large patch like this into the message
without mangling
it. It's very mechanical and I figure everyone actively concerned can
look at the git
branch on sourceware easily enough for themselves.

OK for trunk?


Thanks,
Roland