fpglsl: add some for and while loops

progs/fpglsl/for.glsl

@@ -0,0 +1,11 @@
+uniform int KernelSizeInt;
+
+void main() {
+    int i;
+    vec4 sum = vec4(0.0);
+    for (i = 0; i < KernelSizeInt; ++i) {
+	sum.g += 0.25;
+    }
+    sum.a = 1;
+    gl_FragColor = sum;
+}

progs/fpglsl/while.glsl

@@ -0,0 +1,7 @@
+void main() {
+    float sum = 0.0;
+    while (sum < 0.499999) {
+	sum += 0.1;
+    }
+    gl_FragColor = vec4(sum);
+}