Fix the following error when NDEBUG is defined:

include/llvm/Support/UnicodeCharRanges.h:56:5: error:
use of this statement in a constexpr constructor is a C++1y extension
[-Werror,-Wc++1y-extensions]
     assert(rangesAreValid());
          ^

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189599 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/UnicodeCharRanges.h

@@ -49,9 +49,6 @@ public:
   /// the UnicodeCharSet instance, and should not change. Array is validated by
   /// the constructor, so it makes sense to create as few UnicodeCharSet
   /// instances per each array of ranges, as possible.
-#ifdef NDEBUG
-  LLVM_CONSTEXPR
-#endif
   UnicodeCharSet(CharRanges Ranges) : Ranges(Ranges) {
     assert(rangesAreValid());
   }