Field_varstring: Declare get_data() and get_length() as public

The underlying data members are declared public, so there is no
point in hiding these const accessors.

sql/field.h

@@ -3092,6 +3092,7 @@ class Field_string :public Field_longstr {
 
 
 class Field_varstring :public Field_longstr {
+public:
   uchar *get_data() const
   {
     return ptr + length_bytes;
@@ -3100,7 +3101,6 @@ class Field_varstring :public Field_longstr {
   {
     return length_bytes == 1 ? (uint) *ptr : uint2korr(ptr);
   }
-public:
   /*
     The maximum space available in a Field_varstring, in bytes. See
     length_bytes.