Fix recently introduced compilation error in wxUSE_PALETTE==0 build.

Add missing "#if wxUSE_PALETTE" tests.

Closes #16083.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76146 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Also free internal handlers when wxMSW wxStaticBitmap is destroyed.

r76142 fixed the resource leak when wxStaticBitmap image was replaced by
another one but the leak still happened at the end, when the wxStaticBitmap
was destroyed.

Fix it there as well in the same way.

Closes #16068.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76147 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix showing of 32bpp bitmaps without alpha in wxMSW wxStaticBitmap.

The native control doesn't make a secret copy of the image in this case (0RGB
bitmap, i.e. 32bpp ARGB bitmap with all alpha values set to 0) and just shows
the bitmap we assigned to it directly, so we must not delete it in this case,
otherwise nothing is shown at all.

Closes #16084.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76148 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775