Rename isA to isSameOrDerivedFrom.

There are two evils we can choose from:
- Name overlap between isA-matcher and llvm::isa<>()
- Bad name for what the isA-matcher currently does

After some discussion we have agreed to go with the latter evil.

Review: http://llvm-reviews.chandlerc.com/D40
llvm-svn: 163740
diff --git a/clang/unittests/ASTMatchers/ASTMatchersTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersTest.cpp
index 55e22e9..8b41c96 100644
--- a/clang/unittests/ASTMatchers/ASTMatchersTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersTest.cpp
@@ -106,7 +106,7 @@
   EXPECT_TRUE(notMatches("class Y;", IsDerivedFromX));
   EXPECT_TRUE(notMatches("", IsDerivedFromX));
 
-  DeclarationMatcher IsAX = recordDecl(isA("X"));
+  DeclarationMatcher IsAX = recordDecl(isSameOrDerivedFrom("X"));
 
   EXPECT_TRUE(matches("class X {}; class Y : public X {};", IsAX));
   EXPECT_TRUE(matches("class X {};", IsAX));