Update of the license files

- Fixed the formatting in license text for C/Python 8.0.17 release

- CPYINT branch:53ac01

BUG29521636: Add missing mysqlx_prepare_pb2.py file in MSI product.wxs

Prepare release 8.0.15

BUG29034868: Fix wrong WL number in CHANGES.txt

BUG28673129: Client.close() method raises socket error on Py2.7

A second call to the close method of Client can raise a
sockect error. This seems to be a different behavios in the
sockect library on Python 2.7, This Patch adds a try catch
to avoid raising the error.

This patch also fixes some failing unittests on Pb2 machines.

BUG28443941: differences on pure and c-ext in cmd_change_user()

The invocation of the method cmd_change_user() using the c extension
does not return any status information while the pure python
implementation it does.

This patch adds the missing status results for the cmd_change_user(),
in addition this patchs renames the server_status atribute name to
status_flag from the status information returned from fetch_eof_status()
to be consistent with the name.

Update CPYINT branch

BUG27837814: Fix missing .pyc files in Python 3 commercial packages

Add pip installation instructions in the docs