Problems with OES_EGL_image_external

[eodabash]

I found a couple problems with optimization of shaders that make use of OES_EGL_image_external functionality. The first is that "#extension GL_OES_EGL_image_external : enable" statements don't get printed back in the optimizer output. The second is that texture sampling calls that use a samplerExternalOES sampler seem to get converted to "textureExternal" calls which as far as I can tell is not the correct way to sample from such a sampler (the spec refers to this being an obsolete syntax that was dropped in favor of the existing sampling functions like texture2D).

A test input shader can be found here: https://www.dropbox.com/s/vggjoa1p33uel5n/imageExternal-inES.txt?dl=0