NFC: Remove the ObjC1/ObjC2 distinction from clang (and related projects)

We haven't supported compiling ObjC1 for a long time (and never will again), so
there isn't any reason to keep these separate. This patch replaces
LangOpts::ObjC1 and LangOpts::ObjC2 with LangOpts::ObjC.

Differential revision: https://reviews.llvm.org/D53547

llvm-svn: 345637
diff --git a/clang/lib/Frontend/Rewrite/RewriteModernObjC.cpp b/clang/lib/Frontend/Rewrite/RewriteModernObjC.cpp
index c1abc54..8b27a41 100644
--- a/clang/lib/Frontend/Rewrite/RewriteModernObjC.cpp
+++ b/clang/lib/Frontend/Rewrite/RewriteModernObjC.cpp
@@ -541,7 +541,7 @@
 
     // FIXME: This predicate seems like it would be useful to add to ASTContext.
     bool isObjCType(QualType T) {
-      if (!LangOpts.ObjC1 && !LangOpts.ObjC2)
+      if (!LangOpts.ObjC)
         return false;
 
       QualType OCT = Context->getCanonicalType(T).getUnqualifiedType();