ENOUGH - CONCAT() HACKS. ALSO WRONG
               ERROR MESSAGE WHILE TRYING TO CREATE
               A VIEW ON A NON EXISTING DATABASE

PROBLEM:
The first part of the problem is concluded as not a
bug, as 'concat' is not a reserved word and it is
completely valid to create a view with the name
'concat'.

The second issue is, while trying to create a view on
a non existing database, we are not giving a proper error
message.

FIX:
We have added a check for the database existence while
trying to create a view. This check would give an error
as 'unknown database' when the database does not exist.

This patch is a backport of the patch for Bug#13601606


mysql-test/r/view.result:
  Added test case result of Bug#12626844
mysql-test/t/view.test:
  Added test case for Bug#12626844
sql/sql_view.cc:
  Added a check for database existence in mysql_create_view