[analyzer] Rename generateNode -> addTransition in CheckerContext

Also document addTransition methods.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143059 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/AttrNonNullChecker.cpp b/lib/StaticAnalyzer/Checkers/AttrNonNullChecker.cpp
index fa96d62..8296eb9 100644
--- a/lib/StaticAnalyzer/Checkers/AttrNonNullChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/AttrNonNullChecker.cpp
@@ -125,7 +125,7 @@
 
   // If we reach here all of the arguments passed the nonnull check.
   // If 'state' has been updated generated a new node.
-  C.generateNode(state);
+  C.addTransition(state);
 }
 
 void ento::registerAttrNonNullChecker(CheckerManager &mgr) {