WL#3607: Unify system-table creation among 1)normal, 2)test, 3)windows installers

(Paired with BUG#20166, "mysql-test-run.pl does not test system privilege tables
creation")

To make sure the bootstrap procedure can be performed on all platforms we will
put the system table definitions in .sql file(s) and modify mysqld so it will
take the bootstrap file name(s) as arguments and read directly from them not
requiring the bootstrap commands to be piped from stdin, but of course being
backward compaitble if only --bootstrap is used. This will give all our
installers a common way to boostrap the mysqld from a common set of sql files.

Since we want the ability to insert records in the user tables that contain the
hostname we need to extend the mysqld to have a system variable that reads from
the already existing global variable "glob_hostname", thus making it accessible
from the .sql scripts.

When boostrapping the mysqld there is a small difference between the default
users that we create when running on windows. This can be solved in the same way
as we create the log tables in 5.1, ie. by creating a stored procedure which
have the ability to check the system variable @@version_compile_os to see if the
hist is running on windows.

I will also check why we are actually creating a different set of default user
on windows - maybe that part of the script is obsolete and handled by the
windows installer.

Windows currently uses a Unix box to create the SQL data (in win/data/ , Makefile 
rule "dist-hook") that the installer later loads into the server.  Changing the 
installer should be trivial, and we should be able to remove the make rule also.