Otherwise the alpha channel for bitmaps created directly is empty,
indicating a transparent bitmap (although we don't actually handle
transparency). This complements hardcoding of the alpha channel
in basebmp. VCL bitmaps can be copied bit-for-bit directly into
a basebmp bitmap, hence it's important to make sure we fill the
alpha channel in vcl too.

Conflicts:
	include/vcl/salbtype.hxx

Change-Id: Icb2fa417db6625a6ffa6bd82eb5773ff75be5a3c