Delete Reloc::Default.

Having an enum member named Default is quite confusing: Is it distinct
from the others?

This patch removes that member and instead uses Optional<Reloc> in
places where we have a user input that still hasn't been maped to the
default value, which is now clear has no be one of the remaining 3
options.

llvm-svn: 269988
diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.h b/llvm/lib/Target/PowerPC/PPCTargetMachine.h
index b49c01b..59b4f1e 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.h
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.h
@@ -35,8 +35,9 @@
 
 public:
   PPCTargetMachine(const Target &T, const Triple &TT, StringRef CPU,
-                   StringRef FS, const TargetOptions &Options, Reloc::Model RM,
-                   CodeModel::Model CM, CodeGenOpt::Level OL);
+                   StringRef FS, const TargetOptions &Options,
+                   Optional<Reloc::Model> RM, CodeModel::Model CM,
+                   CodeGenOpt::Level OL);
 
   ~PPCTargetMachine() override;
 
@@ -64,7 +65,7 @@
 public:
   PPC32TargetMachine(const Target &T, const Triple &TT, StringRef CPU,
                      StringRef FS, const TargetOptions &Options,
-                     Reloc::Model RM, CodeModel::Model CM,
+                     Optional<Reloc::Model> RM, CodeModel::Model CM,
                      CodeGenOpt::Level OL);
 };
 
@@ -75,7 +76,7 @@
 public:
   PPC64TargetMachine(const Target &T, const Triple &TT, StringRef CPU,
                      StringRef FS, const TargetOptions &Options,
-                     Reloc::Model RM, CodeModel::Model CM,
+                     Optional<Reloc::Model> RM, CodeModel::Model CM,
                      CodeGenOpt::Level OL);
 };