Don't use wxGenericProgressDialog::m_windowStyle for wxPD_XXX styles.

Don't use wxGenericProgressDialog::m_windowStyle for wxPD_XXX styles.

Storing progress dialog styles in the normal window style didn't work because
they clashed with the TLW styles. The original progress dialog implementation
worked around this by using separate m_has{Abort,Skip}Button variables instead
of relying on wxPD_CAN_{ABORT,SKIP} style bits but this didn't work for the
other styles and was unclear so the new native MSW implementation blithely
used m_windowStyle to test or them and other bits which didn't work at all,
see #12416.

Solve this by using a separate m_pdStyle variable for storing the progress
dialog styles and use it for all wxPD_XXX tests in both the generic and MSW
code. This fixes some bugs (although not all of them yet) and allows to get
rid of m_has{Abort,Skip}Button.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65501 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775