Sprite and RenderTexture blending mode set based off texture premultiplied alpha setting (#20154)

* Added RenderTexture::saveToFileAsNonPMA() to save images without PMA.
Set the PMA parameter to true when calling initWithRawData() inside RenderTexture::newImage(), since textures are PMA.
Renamed Image::premultipliedAlpha() to Image::premultiplyAlpha() to better reflect it's action, and made it public.
Added Image::reversePremultipliedAlpha() to allow the reversing of the PMA.
Updated CCImage-ios.mm to set the correct bitmapInfo for PMA and non-PMA images before saving a file.
Updated RenderTextureTest::RenderTextureSave() to cater for non-PMA file saving.

* [CCImage-ios.mm] Fixed indentation.

* [CCSprite.cpp] Sprite:initWithTexture() should set the blend mode depending on the texture premultiplied alpha setting.
[CCRenderTexture.cpp] Sprite::setOpacityModifyRGB() is set based on the premultiplied alpha setting.

* Fix for incorrect _opacityModifyRGB on non-PMA.

* [CCSprite.cpp] Removed redundant code related to blending mode and opacityModifyRGB when creating a sprite with a texture.

Author: rh101

cocos/2d/CCRenderTexture.cpp

@@ -305,10 +305,11 @@ bool RenderTexture::initWithWidthAndHeight(int w, int h, Texture2D::PixelFormat
 
 #if CC_ENABLE_PREMULTIPLIED_ALPHA != 0
         _sprite->setBlendFunc(BlendFunc::ALPHA_PREMULTIPLIED);
+        _sprite->setOpacityModifyRGB(true);
 #else
         _sprite->setBlendFunc(BlendFunc::ALPHA_NON_PREMULTIPLIED);
+        _sprite->setOpacityModifyRGB(false);
 #endif
-        _sprite->setOpacityModifyRGB(true);
 
         glBindRenderbuffer(GL_RENDERBUFFER, oldRBO);
         glBindFramebuffer(GL_FRAMEBUFFER, _oldFBO);

cocos/2d/CCSprite.cpp

@@ -269,10 +269,6 @@ bool Sprite::initWithTexture(Texture2D *texture, const Rect& rect, bool rotated)
         _recursiveDirty = false;
         setDirty(false);
 
-        _opacityModifyRGB = true;
-
-        _blendFunc = BlendFunc::ALPHA_PREMULTIPLIED;
-
         _flippedX = _flippedY = false;
 
         // default transform anchor: center