Add UnixAPIChecker, a meta checker to include various precondition checks for calls
to various unix/posix functions, e.g. 'open()'.

As a first check, check that when 'open()' is passed 'O_CREAT' that it has
a third argument.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97086 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed