xtstat fails if no PBXT table has been created

Running xtstat on a system with no PBXT table leads to the following error:

$ bin/xtstat --user=root --display=all
Unknown database 'pbxt'

xtstat exits immediately.

Running the following:

$ bin/xtstat --user=root --display=all --database=information_schema

Makes PBXT enter a loop, printing the system parameters.

Suggested fixes:

1. When the pbxt.statistics table does not exist, xtstat, should wait until it is created, and then continue.

2. If the pbxt.statistics table does not exist, then it should be created on the first access.

3. The option --database=information_schema, should set xtstat to use the I_S version of the statistics table table. i.e. SELECT from information_schema.pbxt_statistics instead of pbxt.statistics.

As an alternative to 2, it would be possible to switch automatically to information_schema.pbxt_statistics.