gsdx-ogl: extend HDR colclip to 32 bits texture

Unfortunately 16 bits wasn't enough for Castlevania.

plugins/GSdx/GSRendererOGL.cpp

@@ -959,7 +959,7 @@ void GSRendererOGL::DrawPrims(GSTexture* rt, GSTexture* ds, GSTextureCache::Sour
 	}
 
 	if (ps_sel.hdr) {
-		hdr_rt = dev->CreateTexture(rtsize.x, rtsize.y, GL_RGBA16F);
+		hdr_rt = dev->CreateTexture(rtsize.x, rtsize.y, GL_RGBA32F);
 
 		dev->CopyRectConv(rt, hdr_rt, ComputeBoundingBox(rtscale, rtsize), false);
 

plugins/GSdx/res/glsl/tfx_fs.glsl

@@ -598,6 +598,9 @@ void ps_main()
 
 #if PS_HDR == 1
 	// Use negative value to avoid overflow of the texture (in accumulation mode)
+	// Note: code were initially done for an Half-Float texture. Due to overflow
+	// the texture was upgraded to a full float. Maybe this code is useless now!
+	// Good testcase is castlevania
 	if (any(greaterThan(C.rgb, vec3(128.0f)))) {
 		C.rgb = (C.rgb - 256.0f);
 	}

plugins/GSdx/res/glsl_source.h

@@ -1473,6 +1473,9 @@ static const char* tfx_fs_all_glsl =
 	"\n"
 	"#if PS_HDR == 1\n"
 	"	// Use negative value to avoid overflow of the texture (in accumulation mode)\n"
+	"	// Note: code were initially done for an Half-Float texture. Due to overflow\n"
+	"	// the texture was upgraded to a full float. Maybe this code is useless now!\n"
+	"	// Good testcase is castlevania\n"
 	"	if (any(greaterThan(C.rgb, vec3(128.0f)))) {\n"
 	"		C.rgb = (C.rgb - 256.0f);\n"
 	"	}\n"