This introduces some macros to shorten the code for output of
strings to a file descriptor. I could use this a lot,
but this commit limits itself to the potential buffer overruns
(to ease backporting - provided we want to do this)
Heavy use of the macros probably blows up the code. Perhaps
it would be better to provide e.g. a VG_(write_str3) function
in the tool API.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@6618