gsdx-ogl: add a variable to select FB output

Either 32bits/24bits/16bits

plugins/GSdx/GSDeviceOGL.cpp

@@ -627,6 +627,7 @@ GLuint GSDeviceOGL::CompilePS(PSSelector sel)
 		+ format("#define PS_WMT %d\n", sel.wmt)
 		+ format("#define PS_FMT %d\n", sel.fmt)
 		+ format("#define PS_IFMT %d\n", sel.ifmt)
+		+ format("#define PS_DFMT %d\n", sel.dfmt)
 		+ format("#define PS_AEM %d\n", sel.aem)
 		+ format("#define PS_TFX %d\n", sel.tfx)
 		+ format("#define PS_TCC %d\n", sel.tcc)

plugins/GSdx/GSDeviceOGL.h

@@ -321,7 +321,9 @@ class GSDeviceOGL : public GSDevice
 
 				// Word 2
 				uint32 blend:8;
-				uint32 _free2:24;
+				uint32 dfmt:2;
+
+				uint32 _free2:22;
 			};
 
 			uint64 key;

plugins/GSdx/GSRendererOGL.cpp

@@ -249,6 +249,9 @@ void GSRendererOGL::DrawPrims(GSTexture* rt, GSTexture* ds, GSTextureCache::Sour
 	GSDeviceOGL::OMColorMaskSelector om_csel;
 	GSDeviceOGL::OMDepthStencilSelector om_dssel;
 
+	// Format of the output
+	ps_sel.dfmt = GSLocalMemory::m_psm[context->FRAME.PSM].fmt;
+
 	// Blend
 
 	if (!IsOpaque())