Fix POD for the mysql_init_command

Description of this parameter is confusing, because it uses wrong
name of the parameter: mysql_init_command_timeout instead of
mysql_init_command.
Added ChangeLog entry for mysql_init_command doc fix.
Removed version from example
Synced version in Bundle with DBD
Fixed name in POD.
Moved OSX instructions to INSTALL.pod.
Removed INSTALL.html, moved installation info from README to POD.
This is still needed in Makefile.PL
Render link as link, not as code example.
eval $ExtUtils::MakeMaker::VERSION requires because old ExtUtils::MakeMaker does not eval by itself
Use 'localhost' if testport is set and no testhost

Fixes [RT#83496](https://rt.cpan.org/Ticket/Display.html?id=83496)

I chose to use 'localhost' rather than the 127.0.0.1 suggested
in the report for compatibility reasons - and because of ipv6.