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/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 35ba8c1..a929da4 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -3844,7 +3844,7 @@
 
   case '@':
     // Objective C support.
-    if (CurPtr[-1] == '@' && LangOpts.ObjC1)
+    if (CurPtr[-1] == '@' && LangOpts.ObjC)
       Kind = tok::at;
     else
       Kind = tok::unknown;