Removing LLVM_EXPLICIT, as MSVC 2012 was the last reason for requiring the macro. NFC; LLVM edition.

llvm-svn: 229335
diff --git a/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp b/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
index ce99ee5..16f9adc 100644
--- a/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
@@ -47,7 +47,7 @@
     return *this;
   }
 
-  LLVM_EXPLICIT operator bool() const { return Def || Use; }
+  explicit operator bool() const { return Def || Use; }
 
   // True if the register is defined or used in some form, either directly or
   // via a sub- or super-register.