[coroutines] Rename driver flag -fcoroutines to -fcoroutines-ts

Summary:
Also makes -fcoroutines_ts to be both a Driver and CC1 flag.

Patch mostly by EricWF.

Reviewers: rnk, cfe-commits, rsmith, EricWF

Subscribers: mehdi_amini

Differential Revision: https://reviews.llvm.org/D25130

llvm-svn: 283064
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index d7dccb1..1c3374f 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -526,7 +526,7 @@
   // TS features.
   if (LangOpts.ConceptsTS)
     Builder.defineMacro("__cpp_experimental_concepts", "1");
-  if (LangOpts.Coroutines)
+  if (LangOpts.CoroutinesTS)
     Builder.defineMacro("__cpp_coroutines", "1");
 }