Bug #48888 mysqltest crashes on --replace_result if 'from' is longer than ~1024 symbols

valgrind pointed to a buffer allocated by my_realloc which looked fishy
Replaced size with what was probably intended, added test case.
Now also fixed line after review comment

client/mysqltest.cc

@@ -9452,7 +9452,7 @@ int insert_pointer_name(reg1 POINTER_ARRAY *pa,char * name)
   if (pa->length+length >= pa->max_length)
   {
     if (!(new_pos= (uchar*) my_realloc((uchar*) pa->str,
-				      (uint) (pa->max_length+PS_MALLOC),
+                                      (uint) (pa->length+length+PS_MALLOC),
 				      MYF(MY_WME))))
       DBUG_RETURN(1);
     if (new_pos != pa->str)
@@ -9463,7 +9463,7 @@ int insert_pointer_name(reg1 POINTER_ARRAY *pa,char * name)
 					      char*);
       pa->str=new_pos;
     }
-    pa->max_length+=PS_MALLOC;
+    pa->max_length= pa->length+length+PS_MALLOC;
   }
   if (pa->typelib.count >= pa->max_count-1)
   {

mysql-test/r/mysqltest.result

@@ -417,6 +417,9 @@ mysqltest: At line 1: Wrong number of arguments to replace_column in 'replace_co
 mysqltest: At line 1: Wrong column number to replace_column in 'replace_column a b'
 mysqltest: At line 1: Wrong column number to replace_column in 'replace_column a 1'
 mysqltest: At line 1: Wrong column number to replace_column in 'replace_column 1 b c '
+select "LONG_STRING" as x;
+x
+LONG_STRING
 mysqltest: At line 1: Invalid integer argument "10!"
 mysqltest: At line 1: Invalid integer argument "a"
 mysqltest: At line 1: Missing required argument 'connection name' to command 'connect'

mysql-test/t/mysqltest.test

@@ -1285,6 +1285,17 @@ select "a" as col1, "c" as col2;
 --error 1
 --exec echo "--replace_column 1 b c " | $MYSQL_TEST 2>&1
 
+let $long_rep= 1234567890123456789012345678901234567890;
+let $long_rep= $long_rep,$long_rep;
+let $long_rep= $long_rep,$long_rep;
+let $long_rep= $long_rep,$long_rep;
+let $long_rep= $long_rep,$long_rep;
+let $long_rep= $long_rep,$long_rep;
+
+# This tests from strings > 1024 (here 1311)
+
+--replace_result $long_rep LONG_STRING
+eval select "$long_rep" as x;
 
 # ----------------------------------------------------------------------------
 # Test sync_with_master