Add comment markers in empty lines [ci skip]

range.c

@@ -1879,7 +1879,7 @@ static int r_cover_range_p(VALUE range, VALUE beg, VALUE end, VALUE val);
  *    r.cover?(0)     # => false
  *    r.cover?(5)     # => false
  *    r.cover?('foo') # => false
-
+ *
  *    r = ('a'..'d')
  *    r.cover?('a')     # => true
  *    r.cover?('d')     # => true
@@ -1900,7 +1900,7 @@ static int r_cover_range_p(VALUE range, VALUE beg, VALUE end, VALUE val);
  *    r.cover?(0)     # => false
  *    r.cover?(4)     # => false
  *    r.cover?('foo') # => false
-
+ *
  *    r = ('a'...'d')
  *    r.cover?('a')     # => true
  *    r.cover?('c')     # => true
@@ -1916,7 +1916,7 @@ static int r_cover_range_p(VALUE range, VALUE beg, VALUE end, VALUE val);
  *    r.cover?(0..4)     # => false
  *    r.cover?(1..5)     # => false
  *    r.cover?('a'..'d') # => false
-
+ *
  *    r = (1...4)
  *    r.cover?(1..3)     # => true
  *    r.cover?(1..4)     # => false