progs/glsl: Fix noise GLSL compilation error on Mac OS.
diff --git a/progs/glsl/noise.c b/progs/glsl/noise.c
index bb024b5..1148580 100644
--- a/progs/glsl/noise.c
+++ b/progs/glsl/noise.c
@@ -28,7 +28,7 @@
    "   vec4 p;\n"
    "   p.xy = gl_TexCoord[0].xy;\n"
    "   p.z = Slice;\n"
-   "   p.w = 0;\n"
+   "   p.w = 0.0;\n"
    "   vec4 n = noise4(p * scale);\n"
    "   gl_FragColor = n * Scale + Bias;\n"
    "}\n";