progs/trivial:  Label program windows with actual program name

Each of these programs previously called itself "First Tri" which was a
little confusing.  Could have left one as "First Tri", but the trouble
then is that people would still clone that file & we'd end up with
another thousand first tri apps...
diff --git a/progs/trivial/tri-mask-tri.c b/progs/trivial/tri-mask-tri.c
index 8333f7e..449125a 100644
--- a/progs/trivial/tri-mask-tri.c
+++ b/progs/trivial/tri-mask-tri.c
@@ -143,7 +143,7 @@
 
    glutInitWindowPosition(100, 0); glutInitWindowSize(Width, Height);
    glutInitDisplayMode(type);
-   Win = glutCreateWindow("First Tri");
+   Win = glutCreateWindow(*argv);
    Init();
    glutReshapeFunc(Reshape);
    glutKeyboardFunc(Key);