Add CHARSET keyword (missing from last push)

sql/field.cc:
  Small safety fix

sql/field.cc

@@ -4220,9 +4220,11 @@ void Field_blob::get_key_image(char *buff,uint length)
   char *blob;
   if ((uint32) length > blob_length)
   {
-#ifdef HAVE_purify
+    /*
+      Must clear this as we do a memcmp in opt_range.cc to detect
+      identical keys
+    */
     bzero(buff+2+blob_length, (length-blob_length));
-#endif
     length=(uint) blob_length;
   }
   int2store(buff,length);

sql/lex.h

@@ -80,6 +80,7 @@ static SYMBOL symbols[] = {
   { "CASE",		SYM(CASE_SYM),0,0},
   { "CHAR",		SYM(CHAR_SYM),0,0},
   { "CHARACTER",	SYM(CHAR_SYM),0,0},
+  { "CHARSET",		SYM(CHARSET),0,0},
   { "CHANGE",		SYM(CHANGE),0,0},
   { "CHANGED",		SYM(CHANGED),0,0},
   { "CHECK",		SYM(CHECK_SYM),0,0},