update build documentation for sqldrivers

Hi,

I seem to be missing the "sqldrivers" folder in QtBase git.
It used to be in src\sql\<sqldrivers>, but it's not.

Qt 5.6: http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql?h=5.6 (sqldrivers is there)

Qt 5.7: http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql?h=5.7 (sqldrivers is there)

Qt 5.8: http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql?h=5.8 (no sqldrivers folder)

Qt 5.9: http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql?h=5.9 (no sqldrivers folder)

Even the readme in 5.9 (in src\sql): http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql/README.module talks about: "To compile drivers as dynamically loaded plugins, see the QTDIR/plugins/src/sqldrivers directory."

Did the sqldrivers folder got moved to somewhere else? If so, where?
Or is something seriously wrong since Qt 5.8 (where it went missing apparently)?

Best regards,
Mark

EDIT

Ahh, they went to: http://code.qt.io/cgit/qt/qtbase.git/tree/src/plugins/sqldrivers
Then i guess the README.module and sql.pro file are still wrong: http://code.qt.io/cgit/qt/qtbase.git/tree/src/sql?h=5.9