request single buffered context on windows

Change-Id: I7b9789053872446e312ae4e3c471986e3c5c55d2
windows opengl: Set PFD_DOUBLEBUFFER even for single buffer rendering.

Otherwise I'm getting lots of errers when dealing with virtual devices...

Change-Id: I34e145817d21dfc2d30fa9ffdfedfa714467d105
windows opengl: Explain the concept of the text drawing + minor fixes.

Change-Id: I4651e7e9b8163844be548d4ed975a881d4f83fff
windows opengl: Finally got the text working.

It still does not have a transparent background, but that is pending support in
OpenGLSalGraphicsImpl.

Change-Id: I477a483e6ac940f54f6ffd6816d753d87206bf23
vcl: re-factor image rendering control-flow.

Change-Id: I923f92e5e84d35dafd1c0d1b4d63916ce690cb90
vcldemo: much improved icon rendering tests.

Change-Id: I853bc0a0957cf0db629a0a5f1ced67bc069d8403
vcl: Fix palette modification during BitmapWriteAccess lifetime.

Change-Id: I8bdedd63895ff0b3245d996cf35ac92d9ab0ff9d
vcldemo: dump and render all icons from images.zip when zoomed in.

Change-Id: I89f37b8a1ed70334a3485bc3ca06d04cfe6d0827
opengl: Add many more CHECK_GL_ERROR()'s before returning from functions.

Change-Id: I63c147acf9a4013008b0f6d76867186f04ee57d5
vcldemo: exercise more BitmapEx rendering paths.

Change-Id: Iecd02534dfbe0938a8635e3b7c2363b4531ef5ef
vcldemo: BitmapEx rotation, translation and shear.

Change-Id: I5a44597bc39c6bccfcec32403fae8f8d7d4fe94c

Conflicts:
	vcl/workben/vcldemo.cxx
vcldemo: implement key-bindings and command-line

Change-Id: I98ea70a78f340a2050ef934de3111ba3191ff479

Conflicts:
	vcl/workben/vcldemo.cxx
windows opengl: Do not be _that_ eager with CHECK_GL_ERROR().

Turns out that when you call glGetError() and OpenGL is not yet set up (or
already turned down), it leads to an error; so when we check for errors in a
loop, we never recover from that ;-)

Change-Id: I849ad1dc30fc93ee1c021b446d9ad379bf9987c0
vcl: The backend should decide whether fast alpha drawing is available.

The unx drawAlphaBitmap() already already checks that the source and
destination have the same size.

Windows and OpenGL should be able to handle that without trouble.

OS X would need some additional code, so added an early return for the case
the source and result sizes do not match.

Change-Id: Ib09654aaa9c9064c232cff5094fcaa1190e931c6
opengl: Another places where it is too eager to check for errors.

Change-Id: Ib6ca3d653f3fd1155bce418226146934e765928d
vcl: assert more useful truths on BitmapWriterAccess completion.

Change-Id: I2ccc5eb64bf3b5d5ce94e2ddd4b9b458c3eda217

Conflicts:
	vcl/opengl/salbmp.cxx