Rename class 'CFGReachabilityAnalysis' to 'CFGReverseBlockReachabilityAnalysis'.

This rename serves two purposes:

- It reflects the actual functionality of this analysis.
- We will have more than one reachability analysis.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@127930 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/AnalysisContext.cpp b/lib/Analysis/AnalysisContext.cpp
index 461468d..ddc5e88 100644
--- a/lib/Analysis/AnalysisContext.cpp
+++ b/lib/Analysis/AnalysisContext.cpp
@@ -132,12 +132,12 @@
   return 0;
 }
 
-CFGReachabilityAnalysis *AnalysisContext::getCFGReachablityAnalysis() {
+CFGReverseBlockReachabilityAnalysis *AnalysisContext::getCFGReachablityAnalysis() {
   if (CFA)
     return CFA.get();
   
   if (CFG *c = getCFG()) {
-    CFA.reset(new CFGReachabilityAnalysis(*c));
+    CFA.reset(new CFGReverseBlockReachabilityAnalysis(*c));
     return CFA.get();
   }