Another fix for anisotropic filtering troubles on Linux.

Don't know anymore what's going on - preventing setting anisotropy to 1 in all cases apparently makes failures on Linux go away but this still doesn't explain why original anisotropy example works ok with setting anisotropy to 1.

Please note that there is now extra logic to allow for resetting anisotropy back to 1 (for platforms that don't exhibit this troubles), if we just prevented setting anisotropy to 1 in all cases, reset wouldn't be possible.

src/renderers/WebGLRenderer.js

@@ -6012,7 +6012,12 @@ THREE.WebGLRenderer = function ( parameters ) {
 
 		if ( _glExtensionTextureFilterAnisotropic && texture.type !== THREE.FloatType ) {
 
-			_gl.texParameterf( textureType, _glExtensionTextureFilterAnisotropic.TEXTURE_MAX_ANISOTROPY_EXT, Math.min( texture.anisotropy, _maxAnisotropy ) );
+			if ( texture.anisotropy > 1 || texture.__oldAnisotropy ) {
+
+				_gl.texParameterf( textureType, _glExtensionTextureFilterAnisotropic.TEXTURE_MAX_ANISOTROPY_EXT, Math.min( texture.anisotropy, _maxAnisotropy ) );
+				texture.__oldAnisotropy = texture.anisotropy;
+
+			}
 
 		}