fixes to dtrt with ANSI_STDIO; previously there was gratuitous abuse of

fixes to dtrt with ANSI_STDIO; previously there was gratuitous abuse of
this particular definition, as it was really just detecting the presence
of setvbuf().  Now it does a compile-and-run to check for binary fopen()
availability, and the check for setvbuf() has been moved.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@4030 dc483132-0cff-0310-8789-dd5450dbe970