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
diff --git a/lib/Checker/GRExprEngine.cpp b/lib/Checker/GRExprEngine.cpp
index 7f86319..3872856 100644
--- a/lib/Checker/GRExprEngine.cpp
+++ b/lib/Checker/GRExprEngine.cpp
@@ -318,6 +318,7 @@
   RegisterNoReturnFunctionChecker(Eng);
   RegisterBuiltinFunctionChecker(Eng);
   RegisterOSAtomicChecker(Eng);
+  RegisterUnixAPIChecker(Eng);
 }
 
 GRExprEngine::GRExprEngine(AnalysisManager &mgr, GRTransferFuncs *tf)