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/line-userclip.c b/progs/trivial/line-userclip.c
index ecfd28c..77d8228 100644
--- a/progs/trivial/line-userclip.c
+++ b/progs/trivial/line-userclip.c
@@ -128,7 +128,7 @@
     type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
     glutInitDisplayMode(type);
 
-    if (glutCreateWindow("First Tri") == GL_FALSE) {
+    if (glutCreateWindow(*argv) == GL_FALSE) {
 	exit(1);
     }