Fix walkway and wall trims; not sure why shore frills don't also work

osx/tools/mask.frag

@@ -0,0 +1,15 @@
+uniform sampler2D texture;
+uniform sampler2D mask;
+uniform vec2 offset;
+uniform vec2 src;
+
+void main() {
+	// Lookup the pixels in the textures
+	vec4 maskpix = texture2D(mask, gl_TexCoord[0].xy);
+	vec4 texpix = texture2D(texture, gl_TexCoord[0].xy);
+	
+	// If the mask is black, carry the soruce texture through
+	if(maskpix.rgb == vec3(0.0,0.0,0.0))
+		gl_FragColor = texpix;
+	else gl_FragColor = vec4(0.0,0.0,0.0,0.0);
+}