when index is used

When the table contained TEXT columns with empty contents
('', zero length, but not NULL) _and_ strings starting with
control characters like tabulator or newline, the empty values
were not found in a "records in range" estimate. Hence count(*)
missed these records.

The reason was a different set of search flags used for key
insert and key range estimation.

I decided to fix the set of flags used in range estimation.
Otherwise millions of databases around the world would require
a repair after an upgrade.

The consequence is that the manual must be fixed, which claims
that TEXT columns are compared with "end space padding". This
is true for CHAR/VARCHAR but wrong for TEXT. See also bug 21335.

Using INSERT DELAYED on MERGE tables could lead to table
corruptions.

The manual lists a couple of storage engines, which can be
used with INSERT DELAYED. MERGE is not in this list.

The attempt to try it anyway has not been rejected yet.
This bug was not detected earlier as it can work under
special circumstances. Most notable is low concurrency.

To be safe, this patch rejects any attempt to use INSERT
DELAYED on MERGE tables.

into  bk-internal.mysql.com:/data0/bk/mysql-4.1-opt

into  zippy.cornsilk.net:/home/cmiller/work/mysql/mysql-4.1-maint

into  mysql.com:/home/hf/work/25492/my41-25492

into  mysql.com:/home/tnurnberg/24660/41-24660

ENUMs weren't allowed to have character 0xff, a perfectly good character in some locales.
This was circumvented by mapping 0xff in ENUMs to ',', thereby prevent actual commas from
being used. Now if 0xff makes an appearance, we find a character not used in the enum and
use that as a separator. If no such character exists, we throw an error.

Any solution would have broken some sort of existing behaviour. This solution should
serve both fractions (those with 0xff and those with ',' in their enums), but
WILL REQUIRE A DUMP/RESTORE CYCLE FROM THOSE WITH 0xff IN THEIR ENUMS. :-/
That is, mysqldump with their current server, and restore when upgrading to one with
this patch.

into  siva.hindu.god:/home/tsmith/m/bk/maint/41

into  mysql.com:/home/gluh/MySQL/Merge/4.1-opt

into  poseidon.mysql.com:/home/tomas/mysql-4.1-ndb

into  pilot.mysql.com:/home/msvensson/mysql/mysql-4.1-maint

 - strerror might return NULL on some platforms

into  pilot.mysql.com:/home/msvensson/mysql/mysql-4.1-maint

into  neptunus.(none):/home/msvensson/mysql/mysql-4.1-maint

into  pilot.mysql.com:/home/msvensson/mysql/mysql-4.1-maint

into  pilot.mysql.com:/home/msvensson/mysql/mysql-4.1-maint

 - Backport fix from 5.0

into  mysql.com:/usr/home/ram/work/bug23938/my41-bug23938

into  mysql.com:/usr/home/ram/work/bug10798/my41-bug10798

into  chilla.local:/home/mydev/mysql-4.1-axmrg

added valgrind.supp to EXTRA_SCRIPTS(for pushbuild)

into  mysql.com:/home/ram/work/b26012/b26012.4.1

As we have Field_double::not_fixed we must have Field_double::size_of().

into  dev3-63.(none):/home/zhl/mysql/tree-merge/4.1/mysql-4.1-ndb

into  chilla.local:/home/mydev/mysql-4.1-axmrg

Notes:
This patch doesn't fix all issues in the tree and we need jani's fix for that
This patch shoud not be merged into 5.0

into  chilla.local:/home/mydev/mysql-4.1-axmrg

into  chilla.local:/home/mydev/mysql-4.1-axmrg

into  zippy.cornsilk.net:/home/cmiller/work/mysql/mysql-4.1-maint

into  zippy.cornsilk.net:/home/cmiller/work/mysql/mysql-4.1-maint

into  qualinost.(none):/home/mtaylor/src/mysql-4.1-maint

into  mysql.com:/home/svoj/devel/mysql/WL3567/mysql-4.1-engines

When a merge table is opened compare column and key definition of
underlying tables against column and key definition of merge table.

If any of underlying tables have different column/key definition
refuse to open merge table.

into  mysql.com:/home/ram/work/b19690/b19690.4.1

Depending on the queries we use different data processing methods
and can lose some data in case of double (and decimal in 4.1) fields.

The fix consists of two parts:
1. double comparison changed, now double a is equal to double b 
if (a-b) is less than 5*0.1^(1 + max(a->decimals, b->decimals)). 
For example, if a->decimals==1, b->decimals==2, a==b if (a-b)<0.005
2. if we use a temporary table, store double values there as is 
to avoid any data conversion (rounding).