create RGBA format texture for Mesa GLES when the texture is render target

Only RGBA is attachable to a framebuffer in Mesa OpenGL ES
Use alpha mask texture or software mask when stencil bits = 0 in multisampled render target
enable reuse scratch textures for non-android platforms
optimize clip for GL msaa render targe that has stencil bits
compute clip bounds when raster clip is skipped
bug fix for check shader is a bitmap

If shader is bitmap and paint has MaskFilter, do not batch draw, because
it will mess up the transformation matrix
skip raster clip in setRootDevice and clipRectBounds
create MSAA render target for blur mask texture
add isRRect in SkPath

SkCanvas::drawPath() can be routed to GrOvalRenderer which is faster
route SkGpuDevice::drawPath() to SkGpuDevice::drawRRect()

if path contains only one RRect, we can route drawPath to drawRRect
which is much faster
fix texture red support in mesa gles driver.

Mesa GLES 3.0 does not support GL_EXT_texture_rg
detect mesa opengl es