Bug #8433: Overflow must be an error

All numeric operators and functions on integer, floating point 
and DECIMAL values now throw an 'out of range' error rather 
than returning an incorrect value or NULL,  when the result is 
out of supported range for the corresponding data type. 
 
Some test cases in the test suite had to be updated 
accordingly either because the test case itself relied on a 
value returned in case of a numeric overflow, or because a 
numeric overflow was the root cause of the corresponding bugs. 
The latter tests are no longer relevant, since the expressions 
used to trigger the corresponding bugs are not valid anymore. 
However, such test cases have been adjusted and kept "for the 
record". 

mysql-test/r/func_math.result:
  Added test cases for bug #8433. 
  Updated results of the test case for bug #31236.
mysql-test/r/func_misc.result:
  Streamlined test cases.
mysql-test/r/func_test.result:
  Streamlined test cases.
mysql-test/r/select.result:
  Streamlined test cases.
mysql-test/r/sp.result:
  Streamlined test cases.
mysql-test/r/strict.result:
  Streamlined test cases.
mysql-test/r/type_newdecimal.result:
  Streamlined test cases.
mysql-test/suite/sys_vars/r/sql_slave_skip_counter_basic.result:
  Streamlined test cases.
mysql-test/suite/sys_vars/t/sql_slave_skip_counter_basic.test:
  Streamlined test cases.
mysql-test/t/func_math.test:
  Added test cases for bug #8433. 
  Updated results of the test case for bug #31236.
mysql-test/t/func_misc.test:
  Streamlined test cases.
mysql-test/t/func_test.test:
  Streamlined test cases.
mysql-test/t/select.test:
  Streamlined test cases.
mysql-test/t/sp.test:
  Streamlined test cases.
mysql-test/t/strict.test:
  Streamlined test cases.
mysql-test/t/type_newdecimal.test:
  Streamlined test cases.
sql/item_create.cc:
  Changed Item_func_cot() to be defined as a standalone Item
  rather than a combination of "1 / TAN(x)".
sql/item_func.cc:
  Throw an 'out of range' error rather than returning an  
  incorrect value or NULL,  when the result of a numeric 
  operator or a function is out of supported range for  
  the corresponding data type.
sql/item_func.h:
  Added validation helpers as inline methods of Item_func.
sql/share/errmsg-utf8.txt:
  New ER_DATA_OUT_OF_RANGE error.

mysql-test/r/func_misc.result

@@ -25,9 +25,9 @@ length(uuid())	charset(uuid())	length(unhex(replace(uuid(),_utf8'-',_utf8'')))
 36	utf8	16
 set @a= uuid_short();
 set @b= uuid_short();
-select cast(@a - @b as signed);
-cast(@a - @b as signed)
--1
+select @b - @a;
+@b - @a
+1
 select length(format('nan', 2)) > 0;
 length(format('nan', 2)) > 0
 1