Allow ASCII escape character in printf format strings

[Grant Edwards <grante at visi dot com>]

Attached is a patch that allows the ASCII escape character in
printf format strings.

Not allowing the escape character has caused me problems
several times over the years.  Most recently, it messed up the
line-editing functionality in an SSH library which is using
diag_sprintf to format strings to be sent to the SSH client. I
had fixed this in the string-check routine a few times in the
past, but it keeps getting un-fixed when I upgrade eCos. So,
this time I'm submitting a patch. ;)

Attachment: diag_printf_escape.patch
Description: Text document