This is part 2 of core patch for WL#6030.

      
This patch:
  - introduces the dynamic checking that fields in the result table row
    for INSERT statement don't have default value or
    isn't set inside BEFORE-trigger;
  - adds uniform approach to handling warnings/errors if some fields are missed
    from INSERT statement and these fields doesn't have default values;
  - handles possible missed fields and set error in Diagnostic_area if
    strict_mode is set and IGNORE isn't set in INSERT statement; 
  - modifies guint tests: replaces explicit assignement of pointer value to
    Field::m_null_ptr by call of Field::set_null_ptr();
  - adds tests for wl6030.

Author: Dmitry Shulga

mysql-test/r/insert_select.result

@@ -607,7 +607,6 @@ create table t2(No int not null, Field int not null, Count int not null);
 insert into t2 Select null, Field, Count From t1 Where Month=20030901 and Type=2;
 Warnings:
 Warning	1048	Column 'No' cannot be null
-Warning	1048	Column 'No' cannot be null
 select * from t2;
 No	Field	Count
 0	1	100

mysql-test/r/key.result

@@ -160,7 +160,6 @@ UNIQUE (c,i));
 INSERT INTO t1 (c) VALUES (NULL),(NULL);
 Warnings:
 Warning	1048	Column 'c' cannot be null
-Warning	1048	Column 'c' cannot be null
 SELECT * FROM t1;
 c	i
 	1

mysql-test/r/null.result

@@ -105,31 +105,27 @@ ERROR 23000: Column 'a' cannot be null
 INSERT INTO t1 (a) values (null),(null);
 Warnings:
 Warning	1048	Column 'a' cannot be null
-Warning	1048	Column 'a' cannot be null
 INSERT INTO t1 (b) values (null);
 ERROR 23000: Column 'b' cannot be null
 INSERT INTO t1 (b) values (1/null);
 ERROR 23000: Column 'b' cannot be null
 INSERT INTO t1 (b) values (null),(null);
 Warnings:
 Warning	1048	Column 'b' cannot be null
-Warning	1048	Column 'b' cannot be null
 INSERT INTO t1 (c) values (null);
 ERROR 23000: Column 'c' cannot be null
 INSERT INTO t1 (c) values (1/null);
 ERROR 23000: Column 'c' cannot be null
 INSERT INTO t1 (c) values (null),(null);
 Warnings:
 Warning	1048	Column 'c' cannot be null
-Warning	1048	Column 'c' cannot be null
 INSERT INTO t1 (d) values (null);
 ERROR 23000: Column 'd' cannot be null
 INSERT INTO t1 (d) values (1/null);
 ERROR 23000: Column 'd' cannot be null
 INSERT INTO t1 (d) values (null),(null);
 Warnings:
 Warning	1048	Column 'd' cannot be null
-Warning	1048	Column 'd' cannot be null
 select * from t1;
 a	b	c	d
 	0	0000-00-00 00:00:00	0